Bug 462704

Created attachment 317081 [details]
reproducer

+++ This bug was initially created as a clone of Bug #455060 +++

When the parent process sends a PTRACE_KILL to the child that has been
stopped by SIGTRAP (initiated by PTRACE_TRACEME), the child is not
killed, rather than starts running freely.

This kernel bug is present on FC7, RH 5, 5u1, and 5u2, using x86,
x86-64, or Power processors. On the other hand this problem is not
present on e.g. SUSE 10.1, 10.2, and RH 4u5. This implies to us that
the working systems have kernel equal to or less than 2.6.16. the
failing systems have kernel equal to or newer than 2.6.18.

This problem reproduces with e.g. both gcc and PGI compilers. The
reproducer here uses gcc 4.3.0.

The reproducer package consists of two program's: the 'user' code
simplestat_g.out, and the master 'Debugger' code (test_TV.c). First
the master code forks a child and the child then sets
PTRACE_TRACEME. The child then starts running
exec(./simplestat_g.out). The master waits at wait(), and immediately
sends PTRACE_KILL to the child. As result, the child should exit, and
never actually execute and let loose simplestat_g.out.

We suspect that this might be a race condition in the kernel, possibly
a race condition between setting a SIGKILL signal against the child
process and letting it run so it gets killed.

This kernel problem prevents TotalView Debugger from debugging any
'-static' compiled programs on these platforms. We consider this bug
as a critical bug in the kernel and hope that it would be fixed as a
very high priority.

For more details, please see the reproducer codes, particularly
test_TV.c.

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Reproduce:

# User's prog, w/ (or w/o) -static, e.g. here statically linked
/home/compilers/gnu/gcc/4.3.0/x86_64-linux/bin/gcc -g -static -o
simplestat_g.out simple.c -lm

# Mini Debugger prog, executing simplestat_g and trying to PTRACE_KILL it
/home/compilers/gnu/gcc/4.3.0/x86_64-linux/bin/gcc -o a.out test_TV.c

./a.out

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX


Sample output:

FAILING execution, RH 5u1, x86-64:

rhel51-x8664:/home/seppo/Bugs/Bug_11153 > ./a.out
CHILD: PTRACE_TRACEME at 0 :: return code 0 
PARENT: WAIT status 1407 from PID 28777 
PARENT: status -> CHILD stopped, by signal  5 
PARENT: Sent PTRACE_KILL to 28777 :: return code 0 

 FINISHED 
rhel51-x8664:/home/seppo/Bugs/Bug_11153 > counter 0
counter 1
counter 2
counter 3
counter 4
counter 5
counter 6
counter 7
counter 8
counter 9

rhel51-x8664:/home/seppo/Bugs/Bug_11153 > 

rhel51-x8664:/home/seppo/Bugs/Bug_11153 > uname -a
Linux rhel51-x8664.totalviewtech.com 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:19
EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
rhel51-x8664:/home/seppo/Bugs/Bug_11153 > 



SUCCESFULL execution, SUSE 10 SP1, x86-64:

gari:/home/seppo/Bugs/Bug_11153 > ./a.out
CHILD: PTRACE_TRACEME at 0 :: return code 0 
PARENT: WAIT status 1407 from PID 29369 
PARENT: status -> CHILD stopped, by signal  5 
PARENT: Sent PTRACE_KILL to 29369 :: return code 0 

 FINISHED 
gari:/home/seppo/Bugs/Bug_11153 > uname -a
Linux gari 2.6.16.13-4-smp #1 SMP Wed May 3 04:53:23 UTC 2006 x86_64 x86_64
x86_64 GNU/Linux
gari:/home/seppo/Bugs/Bug_11153 > 
---