Package: libc6 Version: 2.11.2-2 Severity: normal In the attached source code, there is a race condition between bsd_signal and abort. In most instances when the program is run, abort successfully terminates the program with a SIGABRT. However, on a very rare occasion, the program instead terminates with a SIGSEGV. This should not happen, as it contradicts both POSIX 1003.1-2008 and also the abort(3) man page.
Since this condition is very hard to reproduce, I ran it as follows:
for i in `seq 1 100000`; do (ulimit -c unlimited; ./testcase; if [ $? -eq 139
]; then cp core core.segv; fi); done
"gdb ./testcase core.segv" then gives the following:
(gdb) bt full
#0 *__GI_abort () at abort.c:128
act = {__sigaction_handler = {sa_handler = 0, sa_sigaction = 0},
sa_mask = {__val = {18446744073709551615 <repeats 16 times>}},
sa_flags = 0, sa_restorer = 0}
sigs = {__val = {32, 0 <repeats 15 times>}}
#1 0x000000000040067a in main () at testcase.c:23
thrd = 140157473478416
-- System Information:
Debian Release: squeeze/sid
APT prefers unstable
APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.34-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages libc6 depends on:
ii libc-bin 2.11.2-2 Embedded GNU C Library: Binaries
ii libgcc1 1:4.5.0-7 GCC support library
libc6 recommends no packages.
Versions of packages libc6 suggests:
ii cdebconf [debconf-2.0] 0.149 Debian Configuration Management Sy
ii debconf [debconf-2.0] 1.5.32 Debian configuration management sy
pn glibc-doc <none> (no description available)
ii locales 2.11.2-2 Embedded GNU C Library: National L
-- debconf information excluded
--
brian m. carlson / brian with sandals: Houston, Texas, US
+1 832 623 2791 | http://www.crustytoothpaste.net/~bmc | My opinion only
OpenPGP: RSA v4 4096b: 88AC E9B2 9196 305B A994 7552 F1BA 225C 0223 B187
/* Compile with: gcc -g -O3 -pthread -o testcase testcase.c */
#include <signal.h>
#include <stddef.h>
#ifdef NIH
extern void abort(void);
#else
#include <stdlib.h>
#endif
void *ignore_sigabrt(void *dummy)
{
for (;;)
bsd_signal(SIGABRT, SIG_IGN);
}
int main(void)
{
pthread_t thrd;
pthread_create(&thrd, NULL, ignore_sigabrt, NULL);
pthread_detach(thrd);
abort();
return 0;
}
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