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d40ac01cbb
The recursive lock used on abort does not synchronize with a new process
creation (either by fork-like interfaces or posix_spawn ones), nor it
is reinitialized after fork().
Also, the SIGABRT unblock before raise() shows another race condition,
where a fork or posix_spawn() call by another thread, just after the
recursive lock release and before the SIGABRT signal, might create
programs with a non-expected signal mask. With the default option
(without POSIX_SPAWN_SETSIGDEF), the process can see SIG_DFL for
SIGABRT, where it should be SIG_IGN.
To fix the AS-safe, raise() does not change the process signal mask,
and an AS-safe lock is used if a SIGABRT is installed or the process
is blocked or ignored. With the signal mask change removal,
there is no need to use a recursive loc. The lock is also taken on
both _Fork() and posix_spawn(), to avoid the spawn process to see the
abort handler as SIG_DFL.
A read-write lock is used to avoid serialize _Fork and posix_spawn
execution. Both sigaction (SIGABRT) and abort() requires to lock
as writer (since both change the disposition).
The fallback is also simplified: there is no need to use a loop of
ABORT_INSTRUCTION after _exit() (if the syscall does not terminate the
process, the system is broken).
The proposed fix changes how setjmp works on a SIGABRT handler, where
glibc does not save the signal mask. So usage like the below will now
always abort.
static volatile int chk_fail_ok;
static jmp_buf chk_fail_buf;
static void
handler (int sig)
{
if (chk_fail_ok)
{
chk_fail_ok = 0;
longjmp (chk_fail_buf, 1);
}
else
_exit (127);
}
[...]
signal (SIGABRT, handler);
[....]
chk_fail_ok = 1;
if (! setjmp (chk_fail_buf))
{
// Something that can calls abort, like a failed fortify function.
chk_fail_ok = 0;
printf ("FAIL\n");
}
Such cases will need to use sigsetjmp instead.
The _dl_start_profile calls sigaction through _profil, and to avoid
pulling abort() on loader the call is replaced with __libc_sigaction.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
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|---|---|---|
| .. | ||
| bits | ||
| sys | ||
| _Fork.c | ||
| aio_misc.h | ||
| cancellation-pc-check.h | ||
| dl-mutex.c | ||
| dl-thread_gscope_wait.c | ||
| dl-tls_init_tp.c | ||
| dl-tunables.list | ||
| fork.h | ||
| futex-internal.h | ||
| gai_misc.h | ||
| Implies | ||
| internaltypes.h | ||
| jmp-unwind.c | ||
| libc_start_call_main.h | ||
| libc-lock.h | ||
| libc-lockP.h | ||
| lowlevellock-futex.h | ||
| lowlevellock.h | ||
| Makeconfig | ||
| Makefile | ||
| malloc-machine.h | ||
| proc_service.h | ||
| pthread_atfork_compat.h | ||
| pthread_early_init.h | ||
| pthread_mutex_backoff.h | ||
| pthread_mutex_conf.h | ||
| pthread-offsets.h | ||
| pthread.h | ||
| pthreadP.h | ||
| setxid.h | ||
| stdio-lock.h | ||
| Subdirs | ||
| tcb-access.h | ||
| tcb-offsets.h | ||
| thread_db.h | ||
| thread_pointer.h | ||
| timer_routines.h | ||
| tst-mqueue8x.c | ||