Software Diagnostics Library

The set of memory dumps that prompted to introduce Insufficient Memory pattern for stack trace database also prompted to include a variant of Memory Leak pattern related to regions of virtual memory address space. We created this simple modeling application:

int _tmain(int argc, _TCHAR* argv[])
{
	int i,j;

	for (i = 1; i < 1000; ++i)
	{
		for (j = 1; j < 1000; ++j)
		{
			VirtualAlloc(NULL, 0x10000, MEM_RESERVE,
                                     PAGE_EXECUTE_READWRITE);
		}
		getc(stdin);
	}
	return 0;
}

We allocated only reserved memory regions. Committing them would probably at some stage manifest Insufficient Memory patterns for committed memory and physical memory. So we took a few consecutive memory dumps and see the ever increasing number of regions allocated at greater and greater virtual addresses:

0:000> !address
[...]
*        0`04070000        0`04080000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04080000        0`04090000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04090000        0`040a0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`040a0000        0`040b0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`040b0000        0`040c0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`040c0000        0`040d0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`040d0000        0`040e0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`040e0000        0`040f0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`040f0000        0`04100000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04100000        0`04110000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04110000        0`04120000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04120000        0`04130000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04130000        0`04140000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`04140000        0`04260000        0`00120000             MEM_FREE    PAGE_NOACCESS                      Free
[...]

0:000> !address
[...]
*        0`2eec0000        0`2eed0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2eed0000        0`2eee0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2eee0000        0`2eef0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2eef0000        0`2ef00000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef00000        0`2ef10000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef10000        0`2ef20000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef20000        0`2ef30000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef30000        0`2ef40000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef40000        0`2ef50000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef50000        0`2ef60000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef60000        0`2ef70000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef70000        0`2ef80000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef80000        0`2ef90000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2ef90000        0`2efa0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2efa0000        0`2efb0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2efb0000        0`2efc0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2efc0000        0`2efd0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2efd0000        0`2efe0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2efe0000        0`2eff0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2eff0000        0`2f000000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2f000000        0`2f010000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`2f010000        0`2f170000        0`00160000             MEM_FREE    PAGE_NOACCESS                      Free
[...]

0:000> !address
[...]
*        0`697f0000        0`69800000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69800000        0`69810000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69810000        0`69820000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69820000        0`69830000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69830000        0`69840000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69840000        0`69850000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69850000        0`69860000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69860000        0`69870000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69870000        0`69880000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69880000        0`69890000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`69890000        0`698a0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`698a0000        0`699e0000        0`00140000             MEM_FREE    PAGE_NOACCESS                      Free
[...]

0:000> !address
[...]
*        0`c08c0000        0`c08d0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c08d0000        0`c08e0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c08e0000        0`c08f0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c08f0000        0`c0900000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c0900000        0`c0910000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c0910000        0`c0920000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c0920000        0`c0930000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        0`c0930000        0`c0960000        0`00030000             MEM_FREE    PAGE_NOACCESS                      Free
[...]

0:000> !address
[...]
*        1`3d6a0000        1`3d6b0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d6b0000        1`3d6c0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d6c0000        1`3d6d0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d6d0000        1`3d6e0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d6e0000        1`3d6f0000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d6f0000        1`3d700000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d700000        1`3d710000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d710000        1`3d720000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d720000        1`3d730000        0`00010000 MEM_PRIVATE MEM_RESERVE                                    <unclassified>
*        1`3d730000        1`3d7a0000        0`00070000             MEM_FREE    PAGE_NOACCESS                      Free
[...]

0:000> !address -summary

--- Usage Summary ---------------- RgnCount ———– Total Size ——– %ofBusy %ofTotal
Free                                     15      7fe`c275e000 (   7.995 Tb)           99.94%
<unclassified>                        80928        1`3d193000 (   4.955 Gb)  99.86%    0.06%
Image                                    28        0`0034b000 (   3.293 Mb)   0.06%    0.00%
Stack                                     6        0`00200000 (   2.000 Mb)   0.04%    0.00%
MemoryMappedFile                          8        0`001af000 (   1.684 Mb)   0.03%    0.00%
TEB                                       2        0`00004000 (  16.000 kb)   0.00%    0.00%
PEB                                       1        0`00001000 (   4.000 kb)   0.00%    0.00%

--- Type Summary (for busy) ------ RgnCount ----------- Total Size -------- %ofBusy %ofTotal
MEM_PRIVATE                           80936        1`3d397000 (   4.957 Gb)  99.90%    0.06%
MEM_IMAGE                                29        0`0034c000 (   3.297 Mb)   0.06%    0.00%
MEM_MAPPED                                8        0`001af000 (   1.684 Mb)   0.03%    0.00%

--- State Summary ---------------- RgnCount ----------- Total Size -------- %ofBusy %ofTotal
MEM_FREE                                 15      7fe`c275e000 (   7.995 Tb)           99.94%
MEM_RESERVE                           80926        1`3d438000 (   4.957 Gb)  99.91%    0.06%
MEM_COMMIT                               47        0`0045a000 (   4.352 Mb)   0.09%    0.00%

--- Protect Summary (for commit) - RgnCount ----------- Total Size -------- %ofBusy %ofTotal
PAGE_EXECUTE_READ                         4        0`001ef000 (   1.934 Mb)   0.04%    0.00%
PAGE_READONLY                            19        0`001de000 (   1.867 Mb)   0.04%    0.00%
PAGE_READWRITE                           17        0`00080000 ( 512.000 kb)   0.01%    0.00%
PAGE_WRITECOPY                            5        0`00008000 (  32.000 kb)   0.00%    0.00%
PAGE_READWRITE|PAGE_GUARD                 2        0`00005000 (  20.000 kb)   0.00%    0.00%

--- Largest Region by Usage ----------- Base Address -------- Region Size ----------
Free                                      1`3fac7000      7fd`bdc79000 (   7.991 Tb)
<unclassified>                            0`7f0e0000        0`00f00000 (  15.000 Mb)
Image                                     0`77831000        0`00102000 (   1.008 Mb)
Stack                                     0`00170000        0`000fb000 (1004.000 kb)
MemoryMappedFile                          0`7efe5000        0`000fb000 (1004.000 kb)
TEB                                     7ff`fffdc000        0`00002000 (   8.000 kb)
PEB                                     7ff`fffd3000        0`00001000 (   4.000 kb)

Examination of such regions for Execution Residue such as Module Hint may point into further troubleshooting directions especially if live debugging is not possible.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

While working on Insufficient Memory pattern for stack trace database we noticed the expansion of certain memory regions. Of course, after some time expanding region consumes remaining free or reserved space available before some other region. Generalizing from this we may say there can be Insufficient Memory pattern variant for any region expanding region. Region expansion may also be implemented via its move into some over position in memory virtual address space. This movement also has its limits. for example, we created this modeling application and found out it stops reallocating memory long before it reaches 2,000,000,000 byte size:

int _tmain(int argc, _TCHAR* argv[])
{
	int i = 100000000;

	void *p = malloc(i);

	for (i = 200000000; i < 2000000000; i+=100000000)
	{
		p = realloc(p, i);
		getc(stdin);
	}

	return 0;
}

We took memory dumps after each loop iteration and after 6 or 8 iterations the memory size was constant and there were no further reallocations:

0:000> !heap -s
[...]
Virtual block: 0000000006370000 - 0000000006370000 (size 0000000000000000)
[...]

0:000> !address
[...]
+ 0`00550000 0`06370000 0`05e20000 MEM_FREE PAGE_NOACCESS Free
+ 0`06370000 0`1222d000 0`0bebd000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Heap [ID: 0; Handle: 0000000000310000; Type: Large block]
+ 0`1222d000 0`77710000 0`654e3000 MEM_FREE PAGE_NOACCESS Free
+ 0`77710000 0`77711000 0`00001000 MEM_IMAGE MEM_COMMIT PAGE_READONLY Image [kernel32; “C:\windows\system32\kernel32.dll”]
[…]

0:000> !heap -s
[...]
Virtual block: 0000000012230000 - 0000000012230000 (size 0000000000000000)
[...]

0:000> !address
[...]
+ 0`005d0000 0`12230000 0`11c60000 MEM_FREE PAGE_NOACCESS Free
+ 0`12230000 0`2404b000 0`11e1b000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Heap [ID: 0; Handle: 0000000000310000; Type: Large block]
+ 0`2404b000 0`77710000 0`536c5000 MEM_FREE PAGE_NOACCESS Free
+ 0`77710000 0`77711000 0`00001000 MEM_IMAGE MEM_COMMIT PAGE_READONLY Image [kernel32; “C:\windows\system32\kernel32.dll”]
[…]

0:000> !heap -s
[...]
Virtual block: 0000000024050000 - 0000000024050000 (size 0000000000000000)
[...]

0:000> !address
[...]
+ 0`00590000 0`24050000 0`23ac0000 MEM_FREE PAGE_NOACCESS Free
+ 0`24050000 0`3bdc9000 0`17d79000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Heap [ID: 0; Handle: 0000000000310000; Type: Large block]
+ 0`3bdc9000 0`77710000 0`3b947000 MEM_FREE PAGE_NOACCESS Free
+ 0`77710000 0`77711000 0`00001000 MEM_IMAGE MEM_COMMIT PAGE_READONLY Image [kernel32; “C:\windows\system32\kernel32.dll”]
[…]

We skip a few iterations and finally come to a region that will not move and not increase:

0:000> !heap -s
[...]
Virtual block: 0000000041d30000 - 0000000041d30000 (size 0000000000000000)
[...]

0:000> !address
[...]
+ 0`006c0000 0`41d30000 0`41670000 MEM_FREE PAGE_NOACCESS Free
+ 0`41d30000 0`6b8c3000 0`29b93000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Heap [ID: 0; Handle: 0000000000310000; Type: Large block]
+ 0`6b8c3000 0`77710000 0`0be4d000 MEM_FREE PAGE_NOACCESS Free
+ 0`77710000 0`77711000 0`00001000 MEM_IMAGE MEM_COMMIT PAGE_READONLY Image [kernel32; “C:\windows\system32\kernel32.dll”]
[…]

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Once we have seen a sequence of process memory dumps with the largest one almost 4GB. They were all saved from the process with growing memory consumption from 200MB initially. Initially we suspected process heap Memory Leak. However, heap statistics (!heap -s) was normal. There were not even large block allocations. The dumps were also supplied with UMDH logs but their difference only showed Memory Fluctuation and not increase. Stack Trace Collection revealed one Spiking Thread was logging a heap allocation into user mode stack trace database. We could also see that it was Distributed Spike. Inspection of address space showed large number of sequential regions of the same size with Stack Trace Database entries inside. So we concluded that it was stack trace logging Instrumentation Side Effect and advised to limit stack backtrace size in gflags.exe.

To make sure we understood that problem correctly we decided to model it. We didn’t come to the same results probably due to different logging implementation but memory dumps clearly show the possibility of Insufficient Memory pattern variant. Here’s the source code:

void foo20 (int size)
{
    free(malloc(size));
}

#define FOO(x,y) void foo##x (int size) { foo##y(size); }

FOO(19,20)
FOO(18,19)
FOO(17,18)
FOO(16,17)
FOO(15,16)
FOO(14,15)
FOO(13,14)
FOO(12,13)
FOO(11,12)
FOO(10,11)
FOO(9,10)
FOO(8,9)
FOO(7,8)
FOO(6,7)
FOO(5,6)
FOO(4,5)
FOO(3,4)
FOO(2,3)
FOO(1,2)

typedef void (*PFN) (int);

#define ARRSZ 20

PFN pfnArr[ARRSZ]  = {foo1, foo2, foo3, foo4, foo5, foo6, foo7,
    foo8, foo9, foo10, foo11, foo12, foo13, foo14,
    foo15, foo16, foo17, foo18, foo19, foo20};

int _tmain(int argc, _TCHAR* argv[])
{
    int i;

    for (i = 1; i < 1000000000; ++i) 
    {
        pfnArr[i%ARRSZ](i);
    }

    Sleep(-1); 
    return 0;
}

It allocates and then freezes heap entries of different size from 1 byte to 1,000,000,000 bytes all with different 20 possible stack traces. We choose different stack traces to increase the number of different {size, stack backtrace} pairs as several allocation of similar size having the same stack trace may be recorded only once in the database. We emulate different stack traces by calling different entries in pfnArr. Each call then leads to foo20 but the resulting stack trace depth is different. We also enabled “Create user mode stack trace database” checkbox in gflags.exe for our application called AllocFree.exe.

Then we see the expansion of Stack Trace Database regions (addresses are different because memory dumps were taken from different application runs):

0:000> !address
[...]
+ 0`00240000 0`00312000 0`000d2000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Other [Stack Trace Database]
0`00312000 0`01a37000 0`01725000 MEM_PRIVATE MEM_RESERVE Other [Stack Trace Database]
0`01a37000 0`01a40000 0`00009000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Other [Stack Trace Database]

0:000> !address
[...]
+ 0`001b0000 0`0188c000 0`016dc000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Other [Stack Trace Database]
0`0188c000 0`0188d000 0`00001000 MEM_PRIVATE MEM_RESERVE Other [Stack Trace Database]
0`0188d000 0`019b0000 0`00123000 MEM_PRIVATE MEM_COMMIT PAGE_READWRITE Other [Stack Trace Database]

Heap stays the same:

0:000> !heap -s
NtGlobalFlag enables following debugging aids for new heaps:
stack back traces
LFH Key                   : 0x000000f841c4f9c0
Termination on corruption : ENABLED
           Heap     Flags   Reserv  Commit  Virt   Free  List   UCR  Virt  Lock
  Fast
                             (k)     (k)    (k)     (k) length      blocks cont.
 heap
-------------------------------------------------------------------------------
------
0000000001a40000 08000002    4096   1444   4096   1164     4     3    0      0
   LFH
External fragmentation  80 % (4 free blocks)
0000000000010000 08008000      64      4     64      1     1     1    0      0
0000000000020000 08008000      64     64     64     61     1     1    0      0
-------------------------------------------------------------------------------
------

0:000> !heap -s
NtGlobalFlag enables following debugging aids for new heaps:
stack back traces
LFH Key                   : 0x000000473a639107
Termination on corruption : ENABLED
           Heap     Flags   Reserv  Commit  Virt   Free  List   UCR  Virt  Lock
  Fast
                             (k)     (k)    (k)     (k) length      blocks cont.
 heap
-------------------------------------------------------------------------------
------
00000000019c0000 08000002    4096   1444   4096   1164     4     3    0      0
   LFH
External fragmentation  80 % (4 free blocks)
0000000000010000 08008000      64      4     64      1     1     1    0      0
0000000000020000 08008000      64     64     64     61     1     1    0      0
-------------------------------------------------------------------------------
------

But we see the thread consuming much CPU and caught while logging stack backtrace:

0:000> kc
Call Site
ntdll!RtlpStdLogCapturedStackTrace
ntdll!RtlStdLogStackTrace
ntdll!RtlLogStackBackTraceEx
ntdll!RtlpAllocateHeap
ntdll!RtlAllocateHeap
AllocFree!_heap_alloc
AllocFree!malloc
AllocFree!foo20
AllocFree!foo19
AllocFree!foo18
AllocFree!foo17
AllocFree!foo16
AllocFree!foo15
AllocFree!foo14
AllocFree!foo13
AllocFree!foo12
AllocFree!foo11
AllocFree!foo10
AllocFree!foo9
AllocFree!foo8
AllocFree!foo7
AllocFree!foo6
AllocFree!foo5
AllocFree!foo4
AllocFree!foo3
AllocFree!foo2
AllocFree!foo1
AllocFree!wmain
AllocFree!__tmainCRTStartup
kernel32!BaseThreadInitThunk
ntdll!RtlUserThreadStart

0:000> !runaway f
 User Mode Time
  Thread       Time
   0:53b8      0 days 3:22:02.354
 Kernel Mode Time
  Thread       Time
   0:53b8      0 days 0:20:39.022
 Elapsed Time
  Thread       Time
   0:53b8      0 days 10:11:23.596

If we dump some portion of the region we see recorded stack backtraces:

0:000> dps 0`0188c000-200 L200/8
00000000`0188be00 00000000`77891142 ntdll!RtlpAllocateHeap+0x33bd
00000000`0188be08 00000000`778834d8 ntdll!RtlAllocateHeap+0x16c
00000000`0188be10 00000001`3fcc13cb AllocFree!malloc+0x5b
00000000`0188be18 00000001`3fcc1015 AllocFree!foo20+0x15
00000000`0188be20 00000001`3fcc1041 AllocFree!foo19+0x11
00000000`0188be28 00000001`3fcc1061 AllocFree!foo18+0x11
00000000`0188be30 00000001`3fcc12e3 AllocFree!wmain+0x53
00000000`0188be38 00000001`3fcc156c AllocFree!__tmainCRTStartup+0x144
00000000`0188be40 00000000`777259ed kernel32!BaseThreadInitThunk+0xd
00000000`0188be48 00000000`7785c541 ntdll!RtlUserThreadStart+0x1d
00000000`0188be50 00000000`0188b1d0
00000000`0188be58 0009457d`00024fff
00000000`0188be60 00000000`77891142 ntdll!RtlpAllocateHeap+0x33bd
00000000`0188be68 00000000`778834d8 ntdll!RtlAllocateHeap+0x16c
00000000`0188be70 00000001`3fcc13cb AllocFree!malloc+0x5b
00000000`0188be78 00000001`3fcc1015 AllocFree!foo20+0x15
00000000`0188be80 00000001`3fcc1041 AllocFree!foo19+0x11
00000000`0188be88 00000001`3fcc12e3 AllocFree!wmain+0x53
00000000`0188be90 00000001`3fcc156c AllocFree!__tmainCRTStartup+0x144
00000000`0188be98 00000000`777259ed kernel32!BaseThreadInitThunk+0xd
00000000`0188bea0 00000000`7785c541 ntdll!RtlUserThreadStart+0x1d
00000000`0188bea8 00000000`00000000
00000000`0188beb0 00000000`0188b230
00000000`0188beb8 0008457e`00023fff
00000000`0188bec0 00000000`77891142 ntdll!RtlpAllocateHeap+0x33bd
00000000`0188bec8 00000000`778834d8 ntdll!RtlAllocateHeap+0x16c
00000000`0188bed0 00000001`3fcc13cb AllocFree!malloc+0x5b
00000000`0188bed8 00000001`3fcc1015 AllocFree!foo20+0x15
00000000`0188bee0 00000001`3fcc12e3 AllocFree!wmain+0x53
00000000`0188bee8 00000001`3fcc156c AllocFree!__tmainCRTStartup+0x144
00000000`0188bef0 00000000`777259ed kernel32!BaseThreadInitThunk+0xd
00000000`0188bef8 00000000`7785c541 ntdll!RtlUserThreadStart+0x1d
00000000`0188bf00 00000000`0188b280
00000000`0188bf08 001b457f`0002dfff
00000000`0188bf10 00000000`77891142 ntdll!RtlpAllocateHeap+0x33bd
00000000`0188bf18 00000000`778834d8 ntdll!RtlAllocateHeap+0x16c
00000000`0188bf20 00000001`3fcc13cb AllocFree!malloc+0x5b
00000000`0188bf28 00000001`3fcc1015 AllocFree!foo20+0x15
00000000`0188bf30 00000001`3fcc1041 AllocFree!foo19+0x11
00000000`0188bf38 00000001`3fcc1061 AllocFree!foo18+0x11
00000000`0188bf40 00000001`3fcc1081 AllocFree!foo17+0x11
00000000`0188bf48 00000001`3fcc10a1 AllocFree!foo16+0x11
00000000`0188bf50 00000001`3fcc10c1 AllocFree!foo15+0x11
00000000`0188bf58 00000001`3fcc10e1 AllocFree!foo14+0x11
00000000`0188bf60 00000001`3fcc1101 AllocFree!foo13+0x11
00000000`0188bf68 00000001`3fcc1121 AllocFree!foo12+0x11
00000000`0188bf70 00000001`3fcc1141 AllocFree!foo11+0x11
00000000`0188bf78 00000001`3fcc1161 AllocFree!foo10+0x11
00000000`0188bf80 00000001`3fcc1181 AllocFree!foo9+0x11
00000000`0188bf88 00000001`3fcc11a1 AllocFree!foo8+0x11
00000000`0188bf90 00000001`3fcc11c1 AllocFree!foo7+0x11
00000000`0188bf98 00000001`3fcc11e1 AllocFree!foo6+0x11
00000000`0188bfa0 00000001`3fcc1201 AllocFree!foo5+0x11
00000000`0188bfa8 00000001`3fcc1221 AllocFree!foo4+0x11
00000000`0188bfb0 00000001`3fcc1241 AllocFree!foo3+0x11
00000000`0188bfb8 00000001`3fcc1261 AllocFree!foo2+0x11
00000000`0188bfc0 00000001`3fcc1281 AllocFree!foo1+0x11
00000000`0188bfc8 00000001`3fcc12e3 AllocFree!wmain+0x53
00000000`0188bfd0 00000001`3fcc156c AllocFree!__tmainCRTStartup+0x144
00000000`0188bfd8 00000000`777259ed kernel32!BaseThreadInitThunk+0xd
00000000`0188bfe0 00000000`7785c541 ntdll!RtlUserThreadStart+0x1d
00000000`0188bfe8 00000000`00000000
00000000`0188bff0 00000000`00000000
00000000`0188bff8 00000000`00000000

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Sometimes I hear voices saying that Linux, FreeBSD, and Mac OS X core dumps are uninteresting. This is not true. If you haven’t seen anything interesting there it just simply means you have only encountered a limited amount of abnormal software behaviour. The widespread usage of Windows OS means that most patterns have been diagnosed and described first and other OS are waiting their turn.

My goal is to have a pattern catalog with examples from different OS. For example, currently, all Mac OS X patterns I provide are just examples to existing Windows pattern names. All OS share the same structure and behavior, for example, structural memory analysis patterns and the same computational model. Although structural patterns are different from behavioral patterns I also plan to expand the structural list significantly especially in relation to forthcoming Windows malware analysis training. Regarding behavioral patterns it is possible to model and predict specific pattern examples for another OS by using already existing catalog.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Memoretics promotes pattern-driven memory dump and software trace analysis which has many uses but not limited to:

• Software and site reliability
• Software Debugging
• QA and Software Testing
• Computer Security
• Software Troubleshooting
• Malware Research and Analysis
• Tools as a Service (TaaS)
• Supportability
• Software Diagnostics

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Memoretics as a science of memory snapshots borrows many ideas from the following disciplines (the list is not exhaustive):

• Troubleshooting and Debugging
• Intelligence Analysis
• Critical Thinking
• Forensics
• Linguistics
• Archaeology
• Psychoanalysis
• History
• Mathematics: Sets and Categories
• Literary Criticism and Narratology

It also contributes many ideas back. The following diagram depicts such an interaction:

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

As a part of unified debugging pattern and generative debugging approach we extend software behavior analysis patterns such as memory dump and software trace analysis with UI abnormal behaviour patterns. Here by abnormality we mean behavior that users should not encounter while using software. Typical example is some error message or GUI distortion during execution of a functional use case. Such patterns will extend software behavior analysis pattern language we use for description of various post-construction software problems.

The first pattern we start with is called Error Message Box and we link it to Message Box and Self-Diagnosis memory analysis patterns. You can download x86 and x64 modeling examples from this location:

UIPMessageBox.zip

When we start the application it shows a message box:

We then launch Task Manager and find the window:

Then we save a crash dump using right-click context menu:

When we open the process memory dump we see this stack trace:

0:000> ~*kL

.  0  Id: d30.71c Suspend: 0 Teb: 000007ff`fffdd000 Unfrozen
Child-SP          RetAddr           Call Site
00000000`002ff1e8 00000000`77837214 user32!ZwUserWaitMessage+0xa
00000000`002ff1f0 00000000`778374a5 user32!DialogBox2+0x274
00000000`002ff280 00000000`778827f0 user32!InternalDialogBox+0x135
00000000`002ff2e0 00000000`77881ae5 user32!SoftModalMessageBox+0x9b4
00000000`002ff410 00000000`7788133b user32!MessageBoxWorker+0x31d
00000000`002ff5d0 00000000`77881232 user32!MessageBoxTimeoutW+0xb3
00000000`002ff6a0 00000001`3ffa101d user32!MessageBoxW+0×4e
00000000`002ff6e0 00000001`3ffa1039 UIPMessageBox!bar+0×1d
00000000`002ff710 00000001`3ffa1052 UIPMessageBox!foo+0×9
00000000`002ff740 00000001`3ffa11ea UIPMessageBox!wmain+0×12
00000000`002ff770 00000000`7770f56d UIPMessageBox!__tmainCRTStartup+0×15a
00000000`002ff7b0 00000000`77942cc1 kernel32!BaseThreadInitThunk+0xd
00000000`002ff7e0 00000000`00000000 ntdll!RtlUserThreadStart+0×1d

We see there that foo function called bar function which displayed the message box. In real scenarios function name could me more meaningful and give a clue for troubleshooting and debugging in addition to message text:

0:000> ub 00000001`3ffa101d
UIPMessageBox!__unguarded_readlc_active+0xfff:
00000001`3ffa0fff add     byte ptr [rax-7Dh],cl
00000001`3ffa1002 in      al,dx
00000001`3ffa1003 sub     byte ptr [rbp+33h],al
00000001`3ffa1006 leave
00000001`3ffa1007 lea     r8,[UIPMessageBox!__mnames+0×28 (00000001`3ffa83c8)]
00000001`3ffa100e lea     rdx,[UIPMessageBox!__mnames+0×38 (00000001`3ffa83d8)]
00000001`3ffa1015 xor     ecx,ecx
00000001`3ffa1017 call    qword ptr [UIPMessageBox!_imp_MessageBoxW (00000001`3ffa71d8)]

0:000> du 00000001`3ffa83c8
00000001`3ffa83c8  “Problem”

0:000> du 00000001`3ffa83d8
00000001`3ffa83d8  “We have a problem!”

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

I’m pleased to announce that MDAA, Volume 5 is available in PDF format:

www.dumpanalysis.org/Memory+Dump+Analysis+Anthology+Volume+5

It features:

- 25 new crash dump analysis patterns
- 11 new pattern interaction case studies (including software tracing)
- 16 new trace analysis patterns
- 7 structural memory patterns
- 4 modeling case studies for memory dump analysis patterns
- Discussion of 3 common analysis mistakes
- Malware analysis case study
- Computer independent architecture of crash analysis report service
- Expanded coverage of software narratology
- Metaphysical and theological implications of memory dump worldview
- More pictures of memory space and physicalist art
- Classification of memory visualization tools
- Memory visualization case studies
- Close reading of the stories of Sherlock Holmes: Dr. Watson’s observational patterns
- Fully cross-referenced with Volume 1, Volume 2, Volume 3, and Volume 4

Its table of contents is available here:

www.dumpanalysis.org/MDAA/MDA-Anthology-V5-TOC.pdf

Paperback and hardcover versions should be available in a week or two. I also started working on Volume 6 that should be available in November-December.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

The first Webinar to start an in-depth discussion of pattern-driven software troubleshooting, debugging and maintenance:

Date: 25th of March 2011
Time: 18:30 (GMT) 14:30 (EST) 11:30 (PST)
Duration: 60 minutes

Space is limited.
Reserve your Webinar seat now at:
https://www3.gotomeeting.com/register/448268158

Topics include:

• A Short History of DumpAnalysis.org
• Memory Dump Analysis Patterns
• Troubleshooting and Debugging Tools (Debugware) Patterns
• Software Trace Analysis Patterns
• From Software Defects to Software Behavior
• Workaround Patterns
• Structural Memory Patterns
• Memory Analysis Domain Pattern Hierarchy
• New Directions

Prerequisites: experience in software troubleshooting and/or debugging.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

As the new decade is approaching (2011-2020) we would like to make a few previews and predictions:

- Increased complexity of software will bring more methods from biological, social sciences and humanities in addition to existing methods of automated debugging and computer science techniques

- Focus on first fault software problem solving (when aspect)

- Focus on pattern-driven software problem solving (how aspect)

- Fusion of debugging and malware analysis into a unified structural and behavioral pattern framework

- Visual debugging, memory and software trace visualization techniques

- Software maintenance certification

- Focus on domain-driven troubleshooting and debugging tools as a service (debugware TaaS)

- Focus on security issues related to memory dumps and software traces

- New scripting languages and programming language extensions for debugging

- The maturation of the science of memory snapshots and software traces (memoretics)

Imagining is not not limited to the above and more to come and explain in the forthcoming parts.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Five volumes of cross-disciplinary Anthology (dubbed by the author “The Summa Memorianica”) lay the foundation of the scientific discipline of Memoretics (study of computer memory snapshots and their evolution in time) that is also called Memory Dump and Software Trace Analysis.ca

The 5th volume contains revised, edited, cross-referenced, and thematically organized selected DumpAnalysis.org blog posts about crash dump, software trace analysis and debugging written in February 2010 - October 2010 for software engineers developing and maintaining products on Windows platforms, quality assurance engineers testing software on Windows platforms, technical support and escalation engineers dealing with complex software issues, and security researchers, malware analysts and reverse engineers. The fifth volume features:

- 25 new crash dump analysis patterns
- 11 new pattern interaction case studies (including software tracing)
- 16 new trace analysis patterns
- 7 structural memory patterns
- 4 modeling case studies for memory dump analysis patterns
- Discussion of 3 common analysis mistakes
- Malware analysis case study
- Computer independent architecture of crash analysis report service
- Expanded coverage of software narratology
- Metaphysical and theological implications of memory dump worldview
- More pictures of memory space and physicalist art
- Classification of memory visualization tools
- Memory visualization case studies
- Close reading of the stories of Sherlock Holmes: Dr. Watson’s observational patterns
- Fully cross-referenced with Volume 1, Volume 2, Volume 3, and Volume 4

Product information:

• Title: Memory Dump Analysis Anthology, Volume 5
• Author: Dmitry Vostokov
• Language: English
• Product Dimensions: 22.86 x 15.24

• Paperback: 400 pages
• Publisher: Opentask (10 December 2010)
• ISBN-13: 978-1-906717-96-4

• Hardcover: 400 pages
• Publisher: Opentask (10 December 2010)
• ISBN-13: 978-1-906717-97-1

Back cover features memory space art image Hot Computation: Memory on Fire.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Memory Dump Analysis Services (DumpAnalysis.com) organizes a free webinar

Date: 18th of August 2010
Time: 21:00 (BST) 16:00 (Eastern) 13:00 (Pacific)
Duration: 90 minutes

Topics include:

- User vs. kernel vs. physical (complete) memory space
- Challenges of complete memory dump analysis
- Common WinDbg commands
- Patterns
- Common mistakes
- Fiber bundles
- Hands-on exercise: a complete memory dump analysis
- A guide to DumpAnalysis.org case studies

Prerequisites: working knowledge of basic user process and kernel memory dump analysis or live debugging using WinDbg 

The webinar link will be posted before 18th of August on DumpAnalysis.com

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Here we model Message Hooks pattern using MessageHistory tool. It uses window message hooking mechanism to intercept window messages. Download the tool and run either MessageHistory.exe or MessageHistory64.exe and push its Start button. Whenever any process becomes active after that either mhhooks.dll or mhhooks64.dll gets injected into the process virtual address space. Then we run WinDbg x86 or WinDbg x64, run notepad.exe and attach the debugger noninvasively to it:

*** wait with pending attach
Symbol search path is: srv*
Executable search path is:
WARNING: Process 2932 is not attached as a debuggee
         The process can be examined but debug events will not be received
(b74.f44): Wake debugger - code 80000007 (first chance)
USER32!NtUserGetMessage+0xa:
00000000`76f9c92a c3              ret

0:000> .symfix

0:000> .reload

0:000> k
Child-SP          RetAddr           Call Site
00000000`0028f908 00000000`76f9c95e USER32!NtUserGetMessage+0xa
00000000`0028f910 00000000`ff511064 USER32!GetMessageW+0x34
00000000`0028f940 00000000`ff51133c notepad!WinMain+0x182
00000000`0028f9c0 00000000`76e7f56d notepad!DisplayNonGenuineDlgWorker+0x2da
00000000`0028fa80 00000000`770b3281 kernel32!BaseThreadInitThunk+0xd
00000000`0028fab0 00000000`00000000 ntdll!RtlUserThreadStart+0x1d

If we don’t select “Noninvasive” in “Attach to Process” dialog box we need to switch from the debugger injected thread to our main notepad application thread:

0:001> .symfix

0:001> .reload

0:001> k
Child-SP          RetAddr           Call Site
00000000`024bfe18 00000000`77178638 ntdll!DbgBreakPoint
00000000`024bfe20 00000000`76e7f56d ntdll!DbgUiRemoteBreakin+0x38
00000000`024bfe50 00000000`770b3281 kernel32!BaseThreadInitThunk+0xd
00000000`024bfe80 00000000`00000000 ntdll!RtlUserThreadStart+0x1d

0:001> ~0s
USER32!NtUserGetMessage+0xa:
00000000`76f9c92a c3              ret

0:000> k
Child-SP          RetAddr           Call Site
00000000`000af9e8 00000000`76f9c95e USER32!NtUserGetMessage+0xa
00000000`000af9f0 00000000`ff511064 USER32!GetMessageW+0x34
00000000`000afa20 00000000`ff51133c notepad!WinMain+0x182
00000000`000afaa0 00000000`76e7f56d notepad!DisplayNonGenuineDlgWorker+0x2da
00000000`000afb60 00000000`770b3281 kernel32!BaseThreadInitThunk+0xd
00000000`000afb90 00000000`00000000 ntdll!RtlUserThreadStart+0x1d

We then inspect the raw stack data to see any execution residue and find a few related function calls:

0:000> !teb
TEB at 000007fffffdd000
    ExceptionList:        0000000000000000
    StackBase:            0000000000290000
    StackLimit:           000000000027f000
    SubSystemTib:         0000000000000000
    FiberData:            0000000000001e00
    ArbitraryUserPointer: 0000000000000000
    Self:                 000007fffffdd000
    EnvironmentPointer:   0000000000000000
    ClientId:             0000000000000b74 . 0000000000000f44
    RpcHandle:            0000000000000000
    Tls Storage:          000007fffffdd058
    PEB Address:          000007fffffdf000
    LastErrorValue:       0
    LastStatusValue:      c0000034
    Count Owned Locks:    0
    HardErrorMode:        0

0:000> dps 000000000027f000 0000000000290000
[...]
00000000`0028e388  00000000`008bd8e0
00000000`0028e390  00000000`00000000
00000000`0028e398  00000000`00000001
00000000`0028e3a0  00000000`00000282
00000000`0028e3a8  00000000`76f966b2 USER32!SendMessageToUI+0x6a
00000000`0028e3b0  00000000`001406b0
00000000`0028e3b8  00000000`004000f8
00000000`0028e3c0  00000000`00000001
00000000`0028e3c8  00000001`800014b8 mhhooks64!CallWndProc+0×2d8
00000000`0028e3d0  00000000`00000000
00000000`0028e3d8  00000000`002f0664
00000000`0028e3e0  00000000`00000001
00000000`0028e3e8  00000000`76f96a72 USER32!ImeNotifyHandler+0xb4
00000000`0028e3f0  00000000`00000000
00000000`0028e3f8  00000000`004000f8
00000000`0028e400  00000000`00000001
00000000`0028e408  000007fe`ff1213b4 IMM32!CtfImmDispatchDefImeMessage+0×60
00000000`0028e410  00000000`00000000
00000000`0028e418  00000000`002f0664
00000000`0028e420  00000000`00000000
00000000`0028e428  00000000`002f0664
00000000`0028e430  00000000`008bd8e0
00000000`0028e438  00000000`76f96a06 USER32!ImeWndProcWorker+0×3af
00000000`0028e440  00000000`00000282
00000000`0028e448  00000000`00000000
00000000`0028e450  00000000`00000001
00000000`0028e458  00000000`004000f8
00000000`0028e460  00000000`00000000
00000000`0028e468  00000000`00000001
00000000`0028e470  00000000`00000000
00000000`0028e478  00000000`00000000
00000000`0028e480  00000000`00000000
00000000`0028e488  00000000`76f9a078 USER32!_fnDWORD+0×44
00000000`0028e490  00000000`00000000
[…]
00000000`0028f770  00000000`001406b0
00000000`0028f778  000007ff`fffdd000
00000000`0028f780  00000000`0028f8c8
00000000`0028f788  00000000`008bd8e0
00000000`0028f790  00000000`00000018
00000000`0028f798  00000000`76f885a0 USER32!DispatchHookW+0×2c
00000000`0028f7a0  000022b2`00000000
00000000`0028f7a8  00000000`00000001
00000000`0028f7b0  000007fe`ff2d2560 MSCTF!IMCLock::`vftable’
00000000`0028f7b8  00000000`00407c50
00000000`0028f7c0  00000000`000c0e51
00000000`0028f7c8  00000000`00000000
00000000`0028f7d0  00000000`00000000
00000000`0028f7d8  00000000`00000113
00000000`0028f7e0  00000000`00000113
00000000`0028f7e8  00000000`00000001
00000000`0028f7f0  00000000`00000000
00000000`0028f7f8  00000000`76f9c3df USER32!UserCallWinProcCheckWow+0×1cb
00000000`0028f800  00000000`ff510000 notepad!CFileDialogEvents_QueryInterface <PERF> (notepad+0×0)
00000000`0028f808  00000000`00000000
00000000`0028f810  00000000`00000000
00000000`0028f818  00000000`00000000
00000000`0028f820  00000000`00000000
00000000`0028f828  00000000`00000038
00000000`0028f830  00000000`00000000
00000000`0028f838  00000000`00000000
00000000`0028f840  00000000`00000000
00000000`0028f848  00000000`770cfdf5 ntdll!KiUserCallbackDispatcherContinue
00000000`0028f850  00000000`00000048
00000000`0028f858  00000000`00000001
00000000`0028f860  00000000`00000000
[…]

We also see a 3rd-party module in proximity having “hook” in its module name: mhhooks64. We disassemble its address to see yet another message hooking evidence:

0:000> .asm no_code_bytes
Assembly options: no_code_bytes

0:000> ub 00000001`800014b8
mhhooks64!CallWndProc+0×2ae:
00000001`8000148e imul    rcx,rcx,30h
00000001`80001492 lea     rdx,[mhhooks64!sendMessages (00000001`80021030)]
00000001`80001499 mov     dword ptr [rdx+rcx+28h],eax
00000001`8000149d mov     r9,qword ptr [rsp+50h]
00000001`800014a2 mov     r8,qword ptr [rsp+48h]
00000001`800014a7 mov     edx,dword ptr [rsp+40h]
00000001`800014ab mov     rcx,qword ptr [mhhooks64!hCallWndHook (00000001`80021028)]
00000001`800014b2 call    qword ptr [mhhooks64!_imp_CallNextHookEx (00000001`80017280)]

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

We continue our modeling of software behaviour with the ubiquitous Memory Leak (process heap) pattern. Instead of leaking small heap allocations that are easy to debug with user mode stack trace database our model program leaks large heap allocations:

// MemoryLeak-ProcessHeap
// Copyright (c) 2010 Dmitry Vostokov
// GNU GENERAL PUBLIC LICENSE
// http://www.gnu.org/licenses/gpl-3.0.txt

#include <windows.h>

int _tmain(int argc, _TCHAR* argv[])
{
 // create extra 25 heaps initially
 for (int i = 0; i < 25; ++i)
  HeapCreate(0, 0, 0);
 
 // create a heap to leak within
 HANDLE hHeap = HeapCreate(0, 0, 0);

 while (true)
 {
  HeapAlloc(hHeap, 0, 1024*1024);
  Sleep(1000);
 }

 return 0;
}

The program creates extra process heaps to simulate real life heap leaks that usually happen not in a default process heap. Then it slowly leaks 0×100000 bytes every second. The application can be downloaded from here (zip file contains source code, x86 and x64 binaries together with corresponding PDB files):

Download MemoryLeak-ProcessHeap.zip

Here I present the results from x64 Windows Server 2008 R2 but x86 variants (I tested on x86 Vista) should be the same.

First we run the application and save a dump of it after a few seconds (I used Task Manager). Heap statistics shows 9 virtual blocks for the last 0000000001e00000 heap:

0:000> !heap -s
LFH Key                   : 0x000000d529c37801
Termination on corruption : ENABLED
          Heap     Flags   Reserv  Commit  Virt   Free  List   UCR  Virt  Lock  Fast
                            (k)     (k)    (k)     (k) length      blocks cont. heap
————————————————————————————-
00000000002b0000 00000002    1024    164   1024      3     1     1    0      0   LFH
0000000000010000 00008000      64      4     64      1     1     1    0      0     
0000000000020000 00008000      64     64     64     61     1     1    0      0     
0000000000220000 00001002    1088    152   1088      3     2     2    0      0   LFH
0000000000630000 00001002     512      8    512      3     1     1    0      0     
0000000000870000 00001002     512      8    512      3     1     1    0      0     
0000000000ad0000 00001002     512      8    512      3     1     1    0      0     
00000000007e0000 00001002     512      8    512      3     1     1    0      0     
0000000000cc0000 00001002     512      8    512      3     1     1    0      0     
0000000000ed0000 00001002     512      8    512      3     1     1    0      0     
00000000010c0000 00001002     512      8    512      3     1     1    0      0     
00000000005b0000 00001002     512      8    512      3     1     1    0      0     
00000000009f0000 00001002     512      8    512      3     1     1    0      0     
00000000004d0000 00001002     512      8    512      3     1     1    0      0     
0000000000230000 00001002     512      8    512      3     1     1    0      0     
0000000000700000 00001002     512      8    512      3     1     1    0      0     
00000000012d0000 00001002     512      8    512      3     1     1    0      0     
0000000000950000 00001002     512      8    512      3     1     1    0      0     
0000000000b90000 00001002     512      8    512      3     1     1    0      0     
00000000014c0000 00001002     512      8    512      3     1     1    0      0     
0000000000e50000 00001002     512      8    512      3     1     1    0      0     
0000000001020000 00001002     512      8    512      3     1     1    0      0     
00000000016e0000 00001002     512      8    512      3     1     1    0      0     
0000000001940000 00001002     512      8    512      3     1     1    0      0     
0000000001b90000 00001002     512      8    512      3     1     1    0      0     
0000000001200000 00001002     512      8    512      3     1     1    0      0     
0000000000c20000 00001002     512      8    512      3     1     1    0      0     
0000000000db0000 00001002     512      8    512      3     1     1    0      0     
0000000000f50000 00001002     512      8    512      3     1     1    0      0     
Virtual block: 0000000001350000 - 0000000001350000 (size 0000000000000000)
Virtual block: 0000000001540000 - 0000000001540000 (size 0000000000000000)
Virtual block: 0000000001760000 - 0000000001760000 (size 0000000000000000)
Virtual block: 00000000019c0000 - 00000000019c0000 (size 0000000000000000)
Virtual block: 0000000001c10000 - 0000000001c10000 (size 0000000000000000)
Virtual block: 0000000001e80000 - 0000000001e80000 (size 0000000000000000)
Virtual block: 0000000001f90000 - 0000000001f90000 (size 0000000000000000)
Virtual block: 00000000020a0000 - 00000000020a0000 (size 0000000000000000)
Virtual block: 00000000021b0000 - 00000000021b0000 (size 0000000000000000)
0000000001e00000 00001002     512      8    512      3     1     1    9      0     
————————————————————————————-

We then wait for a few minutes and save a memory dump again. Heap statistics clearly shows virtual block leaks because now we 276 of them instead of previous 9 (I skipped most of them in the output below):

0:000> !heap -s
LFH Key                   : 0x000000d529c37801
Termination on corruption : ENABLED
          Heap     Flags   Reserv  Commit  Virt   Free  List   UCR  Virt  Lock  Fast
                            (k)     (k)    (k)     (k) length      blocks cont. heap
————————————————————————————-
00000000002b0000 00000002    1024    164   1024      3     1     1    0      0   LFH
0000000000010000 00008000      64      4     64      1     1     1    0      0     
0000000000020000 00008000      64     64     64     61     1     1    0      0     
0000000000220000 00001002    1088    152   1088      3     2     2    0      0   LFH
0000000000630000 00001002     512      8    512      3     1     1    0      0     
0000000000870000 00001002     512      8    512      3     1     1    0      0     
0000000000ad0000 00001002     512      8    512      3     1     1    0      0     
00000000007e0000 00001002     512      8    512      3     1     1    0      0     
0000000000cc0000 00001002     512      8    512      3     1     1    0      0     
0000000000ed0000 00001002     512      8    512      3     1     1    0      0     
00000000010c0000 00001002     512      8    512      3     1     1    0      0     
00000000005b0000 00001002     512      8    512      3     1     1    0      0     
00000000009f0000 00001002     512      8    512      3     1     1    0      0     
00000000004d0000 00001002     512      8    512      3     1     1    0      0     
0000000000230000 00001002     512      8    512      3     1     1    0      0     
0000000000700000 00001002     512      8    512      3     1     1    0      0     
00000000012d0000 00001002     512      8    512      3     1     1    0      0     
0000000000950000 00001002     512      8    512      3     1     1    0      0     
0000000000b90000 00001002     512      8    512      3     1     1    0      0     
00000000014c0000 00001002     512      8    512      3     1     1    0      0     
0000000000e50000 00001002     512      8    512      3     1     1    0      0     
0000000001020000 00001002     512      8    512      3     1     1    0      0     
00000000016e0000 00001002     512      8    512      3     1     1    0      0     
0000000001940000 00001002     512      8    512      3     1     1    0      0     
0000000001b90000 00001002     512      8    512      3     1     1    0      0     
0000000001200000 00001002     512      8    512      3     1     1    0      0     
0000000000c20000 00001002     512      8    512      3     1     1    0      0     
0000000000db0000 00001002     512      8    512      3     1     1    0      0     
0000000000f50000 00001002     512      8    512      3     1     1    0      0     
Virtual block: 0000000001350000 - 0000000001350000 (size 0000000000000000)
Virtual block: 0000000001540000 - 0000000001540000 (size 0000000000000000)
Virtual block: 0000000001760000 - 0000000001760000 (size 0000000000000000)
Virtual block: 00000000019c0000 - 00000000019c0000 (size 0000000000000000)
[… skipped …]
Virtual block: 00000000131b0000 - 00000000131b0000 (size 0000000000000000)
Virtual block: 00000000132c0000 - 00000000132c0000 (size 0000000000000000)
Virtual block: 00000000133d0000 - 00000000133d0000 (size 0000000000000000)
Virtual block: 00000000134e0000 - 00000000134e0000 (size 0000000000000000)
Virtual block: 00000000135f0000 - 00000000135f0000 (size 0000000000000000)
Virtual block: 0000000013700000 - 0000000013700000 (size 0000000000000000)
Virtual block: 0000000013810000 - 0000000013810000 (size 0000000000000000)
Virtual block: 0000000013920000 - 0000000013920000 (size 0000000000000000)
Virtual block: 0000000013a30000 - 0000000013a30000 (size 0000000000000000)
Virtual block: 0000000013b40000 - 0000000013b40000 (size 0000000000000000)
Virtual block: 0000000013c50000 - 0000000013c50000 (size 0000000000000000)
Virtual block: 0000000013d60000 - 0000000013d60000 (size 0000000000000000)
0000000001e00000 00001002     512      8    512      3     1     1  276      0     
————————————————————————————-

We see that size of these blocks is 0×101000 bytes (with hindsight, extra 1000 is probably bookkeeping info):

0:000> !address 0000000013d60000
 ProcessParametrs 00000000002b1f20 in range 00000000002b0000 00000000002d9000
 Environment 00000000002b1320 in range 00000000002b0000 00000000002d9000
    0000000013d60000 : 0000000013d60000 - 0000000000101000
                    Type     00020000 MEM_PRIVATE
                    Protect  00000004 PAGE_READWRITE
                    State    00001000 MEM_COMMIT
                    Usage    RegionUsageHeap
                    Handle   0000000001e00000

We want to know which thread allocates them and we search for the heap address 0000000001e00000 through virtual memory to find any execution residue on thread raw stacks:

0:000> s -q 0 LFFFFFF 0000000001e00000
00000000`001cf608  00000000`01e00000 00000000`01e00000
00000000`001cf610  00000000`01e00000 00000000`00000858
00000000`001cf630  00000000`01e00000 00000000`0000000a
00000000`001cf6c8  00000000`01e00000 00000000`00000000
00000000`001cf6e0  00000000`01e00000 00000000`01e00a80
00000000`001cf720  00000000`01e00000 00000000`00000020
00000000`001cf778  00000000`01e00000 00000000`01e00000
00000000`001cf780  00000000`01e00000 00000000`00000000
00000000`001cf798  00000000`01e00000 00000000`01e02000
00000000`001cf7b0  00000000`01e00000 02100301`00000000
00000000`001cf7c8  00000000`01e00000 00000000`01c10000
00000000`001cf808  00000000`01e00000 00000000`00000001
00000000`001cf830  00000000`01e00000 00000000`00000002
00000000`001cf940  00000000`01e00000 00000000`00000000
00000000`002d8378  00000000`01e00000 004c0044`005c0064
00000000`01e00028  00000000`01e00000 00000000`01e00000
00000000`01e00030  00000000`01e00000 00000000`00000080

Address range 00000000`001cfxxxx belongs to the main thread:

0:000> kL
Child-SP          RetAddr           Call Site
00000000`001cf898 000007fe`fdd91203 ntdll!NtDelayExecution+0xa
00000000`001cf8a0 00000001`3f39104f KERNELBASE!SleepEx+0xab
00000000`001cf940 00000001`3f3911ea MemoryLeak_ProcessHeap!wmain+0×4f
00000000`001cf970 00000000`778cf56d MemoryLeak_ProcessHeap!__tmainCRTStartup+0×15a
00000000`001cf9b0 00000000`77b03281 kernel32!BaseThreadInitThunk+0xd
00000000`001cf9e0 00000000`00000000 ntdll!RtlUserThreadStart+0×1d

We dump the raw stack fragment now:

0:000> dps 00000000`001cf608 00000000`001cf940
00000000`001cf608  00000000`01e00000
00000000`001cf610  00000000`01e00000
00000000`001cf618  00000000`00000858
00000000`001cf620  00000000`00000000
00000000`001cf628  00000000`77b229ac ntdll!RtlAllocateHeap+0×16c
00000000`001cf630  00000000`01e00000
00000000`001cf638  00000000`0000000a
00000000`001cf640  00000000`00000858
00000000`001cf648  00000000`00000860
00000000`001cf650  00000000`00000000
00000000`001cf658  00000000`001cf740
00000000`001cf660  00000020`00001000
00000000`001cf668  fffff680`01000000
00000000`001cf670  00000001`3f390000 MemoryLeak_ProcessHeap!wmain <PERF> (MemoryLeak_ProcessHeap+0×0)
00000000`001cf678  01000000`00000080
00000000`001cf680  00000000`0000f000
00000000`001cf688  02100210`02100210
00000000`001cf690  00000001`3f390000 MemoryLeak_ProcessHeap!wmain <PERF> (MemoryLeak_ProcessHeap+0×0)
00000000`001cf698  00000000`0000f000
00000000`001cf6a0  00000000`01e01fd0
00000000`001cf6a8  00000000`77b07ff3 ntdll!RtlpCreateUCREntry+0xb3
00000000`001cf6b0  00000000`001cf6b8
00000000`001cf6b8  00000000`01e01fc0
00000000`001cf6c0  00000000`00000080
00000000`001cf6c8  00000000`01e00000
00000000`001cf6d0  00000000`00000000
00000000`001cf6d8  00000000`00000a00
00000000`001cf6e0  00000000`01e00000
00000000`001cf6e8  00000000`01e00a80
00000000`001cf6f0  00000000`0007e000
00000000`001cf6f8  00000000`77b0f2bb ntdll!RtlpInitializeHeapSegment+0×19b
00000000`001cf700  00000000`01e00208
00000000`001cf708  00000000`00000000
00000000`001cf710  00000000`01e00230
00000000`001cf718  00000000`00000000
00000000`001cf720  00000000`01e00000
00000000`001cf728  00000000`00000020
00000000`001cf730  00000000`00000000
00000000`001cf738  00000000`77b0f676 ntdll!RtlpInitializeUCRIndex+0×36
00000000`001cf740  000007ff`00000003
00000000`001cf748  00000000`00000100
00000000`001cf750  00000000`00000000
00000000`001cf758  00000000`00001002
00000000`001cf760  00000000`00001002
00000000`001cf768  00000000`77b0fec9 ntdll!RtlCreateHeap+0×8f7
00000000`001cf770  00000000`01e02000
00000000`001cf778  00000000`01e00000
00000000`001cf780  00000000`01e00000
00000000`001cf788  00000000`00000000
00000000`001cf790  03010301`00000000
00000000`001cf798  00000000`01e00000
00000000`001cf7a0  00000000`01e02000
00000000`001cf7a8  00000000`01e80000
00000000`001cf7b0  00000000`01e00000
00000000`001cf7b8  02100301`00000000
00000000`001cf7c0  00000000`001f0000
00000000`001cf7c8  00000000`01e00000
00000000`001cf7d0  00000000`01c10000
00000000`001cf7d8  00000000`01e02000
00000000`001cf7e0  00000000`00270000
00000000`001cf7e8  03020302`00000230
00000000`001cf7f0  00000000`77be7288 ntdll!RtlpInterceptorRoutines
00000000`001cf7f8  00000000`00000000
00000000`001cf800  00000000`00100010
00000000`001cf808  00000000`01e00000
00000000`001cf810  00000000`00000001
00000000`001cf818  00000000`00100000
00000000`001cf820  00000000`00000000
00000000`001cf828  00000000`77b229ac ntdll!RtlAllocateHeap+0×16c
00000000`001cf830  00000000`01e00000
00000000`001cf838  00000000`00000002
00000000`001cf840  00000000`00100000
00000000`001cf848  00000000`00101000
00000000`001cf850  00000000`00000000
00000000`001cf858  00000000`001cf940
00000000`001cf860  00000000`00000000
00000000`001cf868  0000f577`2bd1e0ff
00000000`001cf870  00000000`ffffffff
00000000`001cf878  00000000`10010011
00000000`001cf880  00000000`c00000bb
00000000`001cf888  00000000`00000000
00000000`001cf890  00000000`00000100
00000000`001cf898  000007fe`fdd91203 KERNELBASE!SleepEx+0xab
00000000`001cf8a0  00000000`001cf958
00000000`001cf8a8  00000000`00000000
00000000`001cf8b0  00000000`00000000
00000000`001cf8b8  00000000`00000012
00000000`001cf8c0  ffffffff`ff676980
00000000`001cf8c8  00000000`001cf8c0
00000000`001cf8d0  00000000`00000048
00000000`001cf8d8  00000000`00000001
00000000`001cf8e0  00000000`00000000
00000000`001cf8e8  00000000`00000000
00000000`001cf8f0  00000000`00000000
00000000`001cf8f8  00000000`00000000
00000000`001cf900  00000000`00000000
00000000`001cf908  00000000`00000000
00000000`001cf910  00000000`00000000
00000000`001cf918  00000000`00000000
00000000`001cf920  00000000`00000000
00000000`001cf928  00000000`00000001
00000000`001cf930  00000000`00000000
00000000`001cf938  00000001`3f39104f MemoryLeak_ProcessHeap!wmain+0×4f
00000000`001cf940  00000000`01e00000

We see traces of RtlAllocateHeap but it could be a coincidence (imagine that we don’t have access to source code and can’t do live debugging to put breakpoints). We advise to enable use mode stack trace database as explained for another example process: CTX106970. Then we launch our application again and save a new user dump. We repeat the same procedure to examine the raw stack:

0:000> !heap -s
NtGlobalFlag enables following debugging aids for new heaps:
    stack back traces
LFH Key                   : 0x000000c21e1b31e6
Termination on corruption : ENABLED
          Heap     Flags   Reserv  Commit  Virt   Free  List   UCR  Virt  Lock  Fast
                            (k)     (k)    (k)     (k) length      blocks cont. heap
-------------------------------------------------------------------------------------
0000000001bc0000 08000002    1024    168   1024      5     1     1    0      0   LFH
0000000000010000 08008000      64      4     64      1     1     1    0      0     
0000000000020000 08008000      64     64     64     61     1     1    0      0     
0000000000100000 08001002    1088    152   1088      2     2     2    0      0   LFH
0000000001d90000 08001002     512      8    512      3     1     1    0      0     
0000000001f90000 08001002     512      8    512      3     1     1    0      0     
00000000021c0000 08001002     512      8    512      3     1     1    0      0     
0000000002130000 08001002     512      8    512      3     1     1    0      0     
0000000002370000 08001002     512      8    512      3     1     1    0      0     
0000000001e80000 08001002     512      8    512      3     1     1    0      0     
0000000000110000 08001002     512      8    512      3     1     1    0      0     
0000000002510000 08001002     512      8    512      3     1     1    0      0     
0000000002760000 08001002     512      8    512      3     1     1    0      0     
0000000001cc0000 08001002     512      8    512      3     1     1    0      0     
0000000002030000 08001002     512      8    512      3     1     1    0      0     
0000000002960000 08001002     512      8    512      3     1     1    0      0     
0000000002670000 08001002     512      8    512      3     1     1    0      0     
0000000002b90000 08001002     512      8    512      3     1     1    0      0     
00000000022f0000 08001002     512      8    512      3     1     1    0      0     
00000000028b0000 08001002     512      8    512      3     1     1    0      0     
0000000001f10000 08001002     512      8    512      3     1     1    0      0     
0000000002450000 08001002     512      8    512      3     1     1    0      0     
00000000025f0000 08001002     512      8    512      3     1     1    0      0     
0000000002a40000 08001002     512      8    512      3     1     1    0      0     
0000000002c90000 08001002     512      8    512      3     1     1    0      0     
0000000002d90000 08001002     512      8    512      3     1     1    0      0     
0000000002e80000 08001002     512      8    512      3     1     1    0      0     
0000000002fc0000 08001002     512      8    512      3     1     1    0      0     
00000000030b0000 08001002     512      8    512      3     1     1    0      0     
Virtual block: 0000000003130000 - 0000000003130000 (size 0000000000000000)
Virtual block: 0000000003240000 - 0000000003240000 (size 0000000000000000)
Virtual block: 0000000003350000 - 0000000003350000 (size 0000000000000000)
Virtual block: 0000000003460000 - 0000000003460000 (size 0000000000000000)
Virtual block: 0000000003570000 - 0000000003570000 (size 0000000000000000)
Virtual block: 0000000003680000 - 0000000003680000 (size 0000000000000000)
Virtual block: 0000000003790000 - 0000000003790000 (size 0000000000000000)
Virtual block: 00000000038a0000 - 00000000038a0000 (size 0000000000000000)
Virtual block: 00000000039b0000 - 00000000039b0000 (size 0000000000000000)
Virtual block: 0000000003ac0000 - 0000000003ac0000 (size 0000000000000000)
Virtual block: 0000000003bd0000 - 0000000003bd0000 (size 0000000000000000)
Virtual block: 0000000003ce0000 - 0000000003ce0000 (size 0000000000000000)
0000000002270000 08001002     512      8    512      3     1     1   12      0     

0:000> s -q 0 LFFFFFF 0000000002270000
00000000`0029f648  00000000`02270000 00000000`000000a8
00000000`0029f660  00000000`02270000 00000000`77b99bc7
00000000`0029f6e8  00000000`02270000 00000000`02270000
00000000`0029f6f0  00000000`02270000 00000000`00000858
00000000`0029f710  00000000`02270000 00000000`0000000a
00000000`0029f758  00000000`02270000 00000000`0029f918
00000000`0029f7c0  00000000`02270000 00000000`03ce0040
00000000`0029f858  00000000`02270000 00000000`02270000
00000000`0029f860  00000000`02270000 00000000`00000000
00000000`0029f878  00000000`02270000 00000000`02272000
00000000`0029f890  00000000`02270000 02100301`00000000
00000000`0029f8f8  00000000`02270000 00000000`03ce0040
00000000`0029fa20  00000000`02270000 00000000`00000000
00000000`01be8a08  00000000`02270000 0064006e`00690057
00000000`02270028  00000000`02270000 00000000`02270000
00000000`02270030  00000000`02270000 00000000`00000080

0:000> dqs 00000000`0029f648 00000000`0029fa20
00000000`0029f648  00000000`02270000
00000000`0029f650  00000000`000000a8
00000000`0029f658  00000000`00000a80
00000000`0029f660  00000000`02270000
00000000`0029f668  00000000`77b99bc7 ntdll!RtlStdLogStackTrace+0x47
00000000`0029f670  00000000`002a0000
00000000`0029f678  00000000`0000007e
00000000`0029f680  00000000`02270a80
00000000`0029f688  00000000`00000000
00000000`0029f690  00000000`02270208
00000000`0029f698  00070000`77b99bc7
00000000`0029f6a0  00000000`77b6cd8a ntdll! ?? ::FNODOBFM::`string'+0xf35a
00000000`0029f6a8  00000000`77b0fd07 ntdll!RtlCreateHeap+0x56e
00000000`0029f6b0  000007fe`fdd9c6a4 KERNELBASE!HeapCreate+0x54
00000000`0029f6b8  00000001`3faa1030 MemoryLeak_ProcessHeap!wmain+0x30
00000000`0029f6c0  00000001`3faa11ea MemoryLeak_ProcessHeap!__tmainCRTStartup+0x15a
00000000`0029f6c8  00000000`778cf56d kernel32!BaseThreadInitThunk+0xd
00000000`0029f6d0  00000000`77be7288 ntdll!RtlpInterceptorRoutines
00000000`0029f6d8  00000000`00000000
00000000`0029f6e0  00000000`00000860
00000000`0029f6e8  00000000`02270000
00000000`0029f6f0  00000000`02270000
00000000`0029f6f8  00000000`00000858
00000000`0029f700  00000000`00000000
00000000`0029f708  00000000`77b229ac ntdll!RtlAllocateHeap+0x16c
00000000`0029f710  00000000`02270000
00000000`0029f718  00000000`0000000a
00000000`0029f720  00000000`00000858
00000000`0029f728  00000000`00000860
00000000`0029f730  00000000`00000000
00000000`0029f738  00000000`0029f820
00000000`0029f740  00000000`77be7288 ntdll!RtlpInterceptorRoutines
00000000`0029f748  00000000`00000002
00000000`0029f750  00000000`00100030
00000000`0029f758  00000000`02270000
00000000`0029f760  00000000`0029f918
00000000`0029f768  00000000`00000020
00000000`0029f770  00000000`00000002
00000000`0029f778  00000000`00000005
00000000`0029f780  00000000`000750f0
00000000`0029f788  00000000`77ba25b2 ntdll!RtlpRegisterStackTrace+0x92
00000000`0029f790  00000000`000750b8
00000000`0029f798  00000000`00000003
00000000`0029f7a0  00000000`00000000
00000000`0029f7a8  00000000`77ad7a0a ntdll!RtlCaptureStackBackTrace+0x4a
00000000`0029f7b0  00000000`00000002
00000000`0029f7b8  00000000`00100030
00000000`0029f7c0  00000000`02270000
00000000`0029f7c8  00000000`03ce0040
00000000`0029f7d0  00000000`00100020
00000000`0029f7d8  00000000`77ba2eb7 ntdll!RtlpStackTraceDatabaseLogPrefix+0x57
00000000`0029f7e0  00000000`03ce0040
00000000`0029f7e8  00000000`00000000
00000000`0029f7f0  00000000`00100020
00000000`0029f7f8  00000000`000750f0
00000000`0029f800  00000000`77b6ed2d ntdll! ?? ::FNODOBFM::`string’+0×1a81b
00000000`0029f808  00000001`3faa1044 MemoryLeak_ProcessHeap!wmain+0×44
00000000`0029f810  00000001`3faa11ea MemoryLeak_ProcessHeap!__tmainCRTStartup+0×15a
00000000`0029f818  00000000`778cf56d kernel32!BaseThreadInitThunk+0xd
00000000`0029f820  00000000`77b03281 ntdll!RtlUserThreadStart+0×1d
00000000`0029f828  00000000`00000100
00000000`0029f830  00000000`00000000
00000000`0029f838  00000000`08001002
00000000`0029f840  00000000`08001002
00000000`0029f848  00000000`77b0fec9 ntdll!RtlCreateHeap+0×8f7
00000000`0029f850  00000000`02272000
00000000`0029f858  00000000`02270000
00000000`0029f860  00000000`02270000
00000000`0029f868  00000000`00000000
00000000`0029f870  03010301`00000000
00000000`0029f878  00000000`02270000
00000000`0029f880  00000000`02272000
00000000`0029f888  00000000`022f0000
00000000`0029f890  00000000`02270000
00000000`0029f898  02100301`00000000
00000000`0029f8a0  00000000`00001000
00000000`0029f8a8  00000000`77b9a886 ntdll!RtlpSetupExtendedBlock+0xc6
00000000`0029f8b0  00000000`00000000
00000000`0029f8b8  00000000`02272000
00000000`0029f8c0  00000000`000b0000
00000000`0029f8c8  03020302`00000230
00000000`0029f8d0  00000000`77be7288 ntdll!RtlpInterceptorRoutines
00000000`0029f8d8  00000000`00000002
00000000`0029f8e0  00000000`77be7288 ntdll!RtlpInterceptorRoutines
00000000`0029f8e8  00000000`00000002
00000000`0029f8f0  00000000`00100030
00000000`0029f8f8  00000000`02270000
00000000`0029f900  00000000`03ce0040
00000000`0029f908  00000000`77b6ed6a ntdll! ?? ::FNODOBFM::`string’+0×1a858
00000000`0029f910  00000000`00000000
00000000`0029f918  00000000`00000000
00000000`0029f920  00000000`00100000
00000000`0029f928  00000000`00101000
00000000`0029f930  00000000`00000020
00000000`0029f938  00000000`00000002
00000000`0029f940  00000000`00000000
00000000`0029f948  0000f569`df709780
00000000`0029f950  00000000`ffffffff
00000000`0029f958  00000000`12010013
00000000`0029f960  00000000`c00000bb
00000000`0029f968  00000000`00000000
00000000`0029f970  00000000`00000100
00000000`0029f978  000007fe`fdd91203 KERNELBASE!SleepEx+0xab
00000000`0029f980  00000000`0029fa38
00000000`0029f988  00000000`00000000
00000000`0029f990  00000000`00000000
00000000`0029f998  00000000`00000012
00000000`0029f9a0  ffffffff`ff676980
00000000`0029f9a8  00000000`0029f9a0
00000000`0029f9b0  00000000`00000048
00000000`0029f9b8  00000000`00000001
00000000`0029f9c0  00000000`00000000
00000000`0029f9c8  00000000`00000000
00000000`0029f9d0  00000000`00000000
00000000`0029f9d8  00000000`00000000
00000000`0029f9e0  00000000`00000000
00000000`0029f9e8  00000000`00000000
00000000`0029f9f0  00000000`00000000
00000000`0029f9f8  00000000`00000000
00000000`0029fa00  00000000`00000000
00000000`0029fa08  00000000`00000001
00000000`0029fa10  00000000`00000000
00000000`0029fa18  00000001`3faa104f MemoryLeak_ProcessHeap!wmain+0×4f
00000000`0029fa20  00000000`02270000

Now we see this stack trace fragment from user mode stack trace database on the raw stack shown above:

00000000`0029f800  00000000`77b6ed2d ntdll! ?? ::FNODOBFM::`string'+0x1a81b
00000000`0029f808  00000001`3faa1044MemoryLeak_ProcessHeap!wmain+0×44
00000000`0029f810  00000001`3faa11ea MemoryLeak_ProcessHeap!__tmainCRTStartup+0×15a
00000000`0029f818  00000000`778cf56d kernel32!BaseThreadInitThunk+0xd
00000000`0029f820  00000000`77b03281 ntdll!RtlUserThreadStart+0×1d

And it looks like HeapAlloc was called from wmain indeed with 0×100000 parameter:

0:000> ub 00000001`3faa1044
MemoryLeak_ProcessHeap!wmain+0x26:
00000001`3faa1026 xor     edx,edx
00000001`3faa1028 xor     ecx,ecx
00000001`3faa102a call    qword ptr [MemoryLeak_ProcessHeap!_imp_HeapCreate (00000001`3faa7000)]
00000001`3faa1030 mov     rbx,rax
00000001`3faa1033 xor     edx,edx
00000001`3faa1035 mov     r8d,100000h
00000001`3faa103b mov     rcx,rbx
00000001`3faa103e call    qword ptr [MemoryLeak_ProcessHeap!_imp_HeapAlloc (00000001`3faa7008)]

0:000> dps 00000001`3faa7008 L1
00000001`3faa7008  00000000`77b21b70 ntdll!RtlAllocateHeap

The stack trace fragment from x86 Vista user dump even more straightforward:

0040fa00 77946e0c ntdll!RtlAllocateHeap+0×1e3
0040fa04 0022103a MemoryLeak_ProcessHeap!wmain+0×3a
0040fa08 7677d0e9 kernel32!BaseThreadInitThunk+0xe
0040fa0c 779219bb ntdll!__RtlUserThreadStart+0×23
0040fa10 7792198e ntdll!_RtlUserThreadStart+0×1b
0040fa14 7798924f ntdll!RtlpLogCapturedStackTrace+0×103

Of course, we could simply disassemble wmain after identifying our thread but in real life functions are longer and leaking allocations could have happened from frames not present on current stack traces.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Due to many requests for memory dumps corresponding to crash dump analysis patterns I’ve started modeling software behaviour and defects. Every pattern will have an example application(s), service(s) or driver(s) or combination of them. Their execution results in memory layout that corresponds to memory or trace analysis patterns. Today we introduce an example model for Multiple Exceptions (user mode) pattern. The following source code models 3 threads each having an exception during their execution on Windows XP, Windows 7 and Windows Server 2008 R2:

// MultipleExceptions-UserMode
// Copyright (c) 2010 Dmitry Vostokov
// GNU GENERAL PUBLIC LICENSE
// http://www.gnu.org/licenses/gpl-3.0.txt

#include <windows.h>
#include <process.h>

void thread_one(void *)
{
 *(int *)NULL = 0;
}

void thread_two(void *)
{
 *(int *)NULL = 0;
}

int main(int argc, WCHAR* argv[])
{
 _beginthread(thread_two, 0, NULL);
 _beginthread(thread_one, 0, NULL);

 DebugBreak();

 return 0;
}

In fact, thread_one and thread_two can be replaced with just one function because they are identical. Visual C++ compiler does that during code optimization. On Windows 7 and W2K8 R2 I created LocalDumps registry key to save full crash dumps. On Windows XP I set Dr. Watson as a postmortem debugger (via drwtsn32 -i command and configured it to save full user dumps via drwtsn32 command that brings Dr. Watson GUI). Vista had some peculiar behaviour so I postponed its discussion for another post. The application can be downloaded from here (zip file contains source code, x86 and x64 binaries together with corresponding PDB files):

Download MultipleExceptions-UserMode.zip

Now I provide modeling results for x64 W2K8 R2 running on 2 processor machine. Windows 7 and Windows XP results are very similar. If we run x64 executable it crashes and a dump file is saved (x86 crash dump is similar). Default analysis command gives these results:

0:000> !analyze -v

[...]

FAULTING_IP:
MultipleExceptions_UserMode!thread_two+0
00000001`3f8b1000 c704250000000000000000 mov dword ptr [0],0

EXCEPTION_RECORD:  ffffffffffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 000007fefddc2442 (KERNELBASE!DebugBreak+0x0000000000000002)
   ExceptionCode: 80000003 (Break instruction exception)
  ExceptionFlags: 00000000
NumberParameters: 1
   Parameter[0]: 0000000000000000

[...]

ERROR_CODE: (NTSTATUS) 0x80000003 - {EXCEPTION}  Breakpoint  A breakpoint has been reached.

[...]

PRIMARY_PROBLEM_CLASS:  STATUS_BREAKPOINT

[...]

STACK_TEXT: 
00000001`3f8b1000 MultipleExceptions_UserMode!thread_two+0x0
00000001`3f8b10eb MultipleExceptions_UserMode!_callthreadstart+0x17
00000001`3f8b1195 MultipleExceptions_UserMode!_threadstart+0x95
00000000`778cf56d kernel32!BaseThreadInitThunk+0xd
00000000`77b03281 ntdll!RtlUserThreadStart+0x1d

[...]

We see debug break on the first thread:

0:000> kL
Child-SP          RetAddr           Call Site
00000000`002eec78 000007fe`fdd913a6 ntdll!NtWaitForMultipleObjects+0xa
00000000`002eec80 00000000`778d3143 KERNELBASE!WaitForMultipleObjectsEx+0xe8
00000000`002eed80 00000000`77949025 kernel32!WaitForMultipleObjectsExImplementation+0xb3
00000000`002eee10 00000000`779491a7 kernel32!WerpReportFaultInternal+0x215
00000000`002eeeb0 00000000`779491ff kernel32!WerpReportFault+0x77
00000000`002eeee0 00000000`7794941c kernel32!BasepReportFault+0x1f
00000000`002eef10 00000000`77b6573c kernel32!UnhandledExceptionFilter+0x1fc
00000000`002eeff0 00000000`77ae5148 ntdll! ?? ::FNODOBFM::`string'+0x2365
00000000`002ef020 00000000`77b0554d ntdll!_C_specific_handler+0x8c
00000000`002ef090 00000000`77ae5d1c ntdll!RtlpExecuteHandlerForException+0xd
00000000`002ef0c0 00000000`77b1fe48 ntdll!RtlDispatchException+0x3cb
00000000`002ef7a0 000007fe`fddc2442 ntdll!KiUserExceptionDispatcher+0x2e
00000000`002efd58 00000001`3f8b103c KERNELBASE!DebugBreak+0×2
00000000`002efd60 00000001`3f8b13fb MultipleExceptions_UserMode!main+0×2c
00000000`002efd90 00000000`778cf56d MultipleExceptions_UserMode!__tmainCRTStartup+0×15b
00000000`002efdd0 00000000`77b03281 kernel32!BaseThreadInitThunk+0xd
00000000`002efe00 00000000`00000000 ntdll!RtlUserThreadStart+0×1d

2 other threads show exception processing too:

0:000> ~1s; kL
ntdll!NtDelayExecution+0xa:
00000000`77b201fa c3              ret
Child-SP          RetAddr           Call Site
00000000`0076ef78 000007fe`fdd91203 ntdll!NtDelayExecution+0xa
00000000`0076ef80 00000000`77949175 KERNELBASE!SleepEx+0xab
00000000`0076f020 00000000`779491ff kernel32!WerpReportFault+0×45
00000000`0076f050 00000000`7794941c kernel32!BasepReportFault+0×1f
00000000`0076f080 00000000`77b6573c kernel32!UnhandledExceptionFilter+0×1fc
00000000`0076f160 00000000`77ae5148 ntdll! ?? ::FNODOBFM::`string’+0×2365
00000000`0076f190 00000000`77b0554d ntdll!_C_specific_handler+0×8c
00000000`0076f200 00000000`77ae5d1c ntdll!RtlpExecuteHandlerForException+0xd
00000000`0076f230 00000000`77b1fe48 ntdll!RtlDispatchException+0×3cb
00000000`0076f910 00000001`3f8b1000 ntdll!KiUserExceptionDispatcher+0×2e
00000000`0076fec8 00000001`3f8b10eb MultipleExceptions_UserMode!thread_two
00000000`0076fed0 00000001`3f8b1195 MultipleExceptions_UserMode!_callthreadstart+0×17
00000000`0076ff00 00000000`778cf56d MultipleExceptions_UserMode!_threadstart+0×95
00000000`0076ff30 00000000`77b03281 kernel32!BaseThreadInitThunk+0xd
00000000`0076ff60 00000000`00000000 ntdll!RtlUserThreadStart+0×1d

0:001> ~2s; kL
ntdll!NtDelayExecution+0xa:
00000000`77b201fa c3              ret
Child-SP          RetAddr           Call Site
00000000`0086e968 000007fe`fdd91203 ntdll!NtDelayExecution+0xa
00000000`0086e970 00000000`77949175 KERNELBASE!SleepEx+0xab
00000000`0086ea10 00000000`779491ff kernel32!WerpReportFault+0×45
00000000`0086ea40 00000000`7794941c kernel32!BasepReportFault+0×1f
00000000`0086ea70 00000000`77b6573c kernel32!UnhandledExceptionFilter+0×1fc
00000000`0086eb50 00000000`77ae5148 ntdll! ?? ::FNODOBFM::`string’+0×2365
00000000`0086eb80 00000000`77b0554d ntdll!_C_specific_handler+0×8c
00000000`0086ebf0 00000000`77ae5d1c ntdll!RtlpExecuteHandlerForException+0xd
00000000`0086ec20 00000000`77b1fe48 ntdll!RtlDispatchException+0×3cb
00000000`0086f300 00000001`3f8b1000 ntdll!KiUserExceptionDispatcher+0×2e
00000000`0086f8b8 00000001`3f8b10eb MultipleExceptions_UserMode!thread_two
00000000`0086f8c0 00000001`3f8b1195 MultipleExceptions_UserMode!_callthreadstart+0×17
00000000`0086f8f0 00000000`778cf56d MultipleExceptions_UserMode!_threadstart+0×95
00000000`0086f920 00000000`77b03281 kernel32!BaseThreadInitThunk+0xd
00000000`0086f950 00000000`00000000 ntdll!RtlUserThreadStart+0×1d

We look at unhandled exception filter parameter to get exception pointers information:

0:002> kv
Child-SP          RetAddr           : Args to Child                                                           : Call Site
[...]
00000000`0086ea70 00000000`77b6573c : 00000000`0086ebb0 00000000`00000006 00000001`00000000 00000000`00000001 : kernel32!UnhandledExceptionFilter+0×1fc

0:002> .exptr 00000000`0086ebb0

----- Exception record at 00000000`0086f7f0:
ExceptionAddress: 000000013f8b1000 (MultipleExceptions_UserMode!thread_two)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 0000000000000001
   Parameter[1]: 0000000000000000
Attempt to write to address 0000000000000000

----- Context record at 00000000`0086f300:
rax=00000000000ef0b0 rbx=00000000000ef0b0 rcx=0000000000000000
rdx=0000000000000000 rsi=0000000000000000 rdi=0000000000000000
rip=000000013f8b1000 rsp=000000000086f8b8 rbp=0000000000000000
 r8=000007fffffda000  r9=0000000000000000 r10=0000000000000045
r11=000007fffffd9328 r12=0000000000000000 r13=0000000000000000
r14=0000000000000000 r15=0000000000000000
iopl=0         nv up ei pl nz na pe nc
cs=0033  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010202
MultipleExceptions_UserMode!thread_two:
00000001`3f8b1000 c704250000000000000000 mov dword ptr [0],0 ds:00000000`00000000=????????

What we now see that default analysis command showed the break instruction exception record and error code from the first thread but IP and stack trace from other threads having NULL pointer access violation exception.

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -