LI80715: CRASH IN PTHREAD_EXIT STACK UNWINDING WHEN COMPILED WITH -FSTACK-PROTECTOR-STRONG

APAR status

• Closed as program error.

Error description

• After a call to pthread_exit in an application compiled with the
  stack protect -fstack-protector-strong option, the program
  encounters a segmentation fault during the thread stack frame
  unwinding process.  The GDB stack trace may look similar to:
  
  #0  0x00003fffb7d3b4cc in ?? () from
              /lib/powerpc64le-linux-gnu/libgcc_s.so.1
  
  #1  0x00003fffb7d3b968 in ?? () from
              /lib/powerpc64le-linux-gnu/libgcc_s.so.1
  
  #2  0x00003fffb7d3bce0 in ?? () from
              /lib/powerpc64le-linux-gnu/libgcc_s.so.1
  
  #3  0x00003fffb7d3c378 in _Unwind_ForcedUnwind () from
              /lib/powerpc64le-linux-gnu/libgcc_s.so.1
  
  #4  0x00003fffb7f4762c in _Unwind_ForcedUnwind (exc=<optimized
              out>, stop=<optimized out>, stop_argument=<optimized
              out>) at ../sysdeps/nptl/unwind-forcedunwind.c:134
  
  #5  0x00003fffb7f443ec in __GI___pthread_unwind (buf=<optimized
              out>) at unwind.c:121
  
  #6  0x00003fffb7f39424 in __do_cancel () at pthreadP.h:283
  
  #7  __pthread_exit (value=<optimized out>) at pthread_exit.c:28
  

Local fix

• Do no use -fstack-protector-strong
  

Problem summary

• PROBLEM DESCRIPTION:
  The ehframe saved on the stack was corrupted by the store of
  the stack guard canary value.  When unwinding happens, a crash
  occurs.
  
  USERS AFFECTED:
  Users of -fstack-protector-strong and pthreads.
  

Problem conclusion

• The store of the canary word was corrected and the generated
  frame is now safe for unwinding.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  XL C/C++ LINUX

• Fixed component ID

  5725C7310

Applicable component levels