[Bug 1188334] Re: Valgrind SIGSEV with a weird bug

[Julian Taylor]

I think this is the normal behavior of valgrind, it gave you all
information it can provide just propagates the signal.

the issue is in your program, you are corrupting the stack in the second
pop, so the destroy of head is invalid.

** Changed in: valgrind (Ubuntu)
       Status: New => Invalid

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Title:
  Valgrind SIGSEV with a weird bug

Status in “valgrind” package in Ubuntu:
  Invalid

Bug description:
  I made a simple program that make a thread_safe stack.
  My program segfault at the end at stack_destroy (line 118) but I can't figure out why.
  I lauchned it with gdb and it told me that the line 118 did a segfault.
  Then I used valgrind and valgrind segfaulted.

  Steps to reproduce:
  $ gcc thread_stack.c -Wall -o thread_stack -pthread -g
  $ valgrind ./thread_stack

  What I get:
  $ ./thread_stack
  ret is 0
  ret is 1
  make: *** [run] Segmentation fault (core dumped)
  $ valgrind ./thread_stack
  ==25938== Memcheck, a memory error detector
  ==25938== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
  ==25938== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
  ==25938== Command: ./thread_stack
  ==25938== 
  ret is 0
  ret is 1
  ==25938== Invalid read of size 8
  ==25938==    at 0x400A5B: stack_destroy (thread_stack.c:118)
  ==25938==    by 0x400CB8: main (thread_stack.c:203)
  ==25938==  Address 0x2f is not stack'd, malloc'd or (recently) free'd
  ==25938== 
  ==25938== 
  ==25938== Process terminating with default action of signal 11 (SIGSEGV)
  ==25938==  Access not within mapped region at address 0x2F
  ==25938==    at 0x400A5B: stack_destroy (thread_stack.c:118)
  ==25938==    by 0x400CB8: main (thread_stack.c:203)
  ==25938==  If you believe this happened as a result of a stack
  ==25938==  overflow in your program's main thread (unlikely but
  ==25938==  possible), you can try to increase the size of the
  ==25938==  main thread stack using the --main-stacksize= flag.
  ==25938==  The main thread stack size used in this run was 8388608.
  ==25938== 
  ==25938== HEAP SUMMARY:
  ==25938==     in use at exit: 48 bytes in 1 blocks
  ==25938==   total heap usage: 3 allocs, 2 frees, 80 bytes allocated
  ==25938== 
  ==25938== LEAK SUMMARY:
  ==25938==    definitely lost: 48 bytes in 1 blocks
  ==25938==    indirectly lost: 0 bytes in 0 blocks
  ==25938==      possibly lost: 0 bytes in 0 blocks
  ==25938==    still reachable: 0 bytes in 0 blocks
  ==25938==         suppressed: 0 bytes in 0 blocks
  ==25938== Rerun with --leak-check=full to see details of leaked memory
  ==25938== 
  ==25938== For counts of detected and suppressed errors, rerun with: -v
  ==25938== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2)
  Segmentation fault (core dumped)
  $ gdb thread_stack 
  GNU gdb (GDB) 7.5.91.20130417-cvs-ubuntu
  Copyright (C) 2013 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  and "show warranty" for details.
  This GDB was configured as "x86_64-linux-gnu".
  For bug reporting instructions, please see:
  <http://www.gnu.org/software/gdb/bugs/>...
  Reading symbols from /home/blegat/Documents/UCL/q4/os/Examens/thread_stack...done.
  (gdb) run
  Starting program: /home/blegat/Documents/UCL/q4/os/Examens/thread_stack 
  warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7ffff7ffa000
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  ret is 0
  ret is 1

  Program received signal SIGSEGV, Segmentation fault.
  0x0000000000400a5b in stack_destroy (stack=0x7fff) at thread_stack.c:118
  118	  if (stack->first != NULL) {
  (gdb) quit
  A debugging session is active.

          Inferior 1 [process 25961] will be killed.

  Quit anyway? (y or n) y

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: valgrind 1:3.8.1-1ubuntu5
  ProcVersionSignature: Ubuntu 3.8.0-22.33-generic 3.8.11
  Uname: Linux 3.8.0-22-generic x86_64
  ApportVersion: 2.9.2-0ubuntu8
  Architecture: amd64
  Date: Thu Jun  6 20:33:39 2013
  InstallationDate: Installed on 2012-04-26 (405 days ago)
  InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
  MarkForUpload: True
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: valgrind
  UpgradeStatus: Upgraded to raring on 2013-04-27 (40 days ago)

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