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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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| .. | ||
| types | ||
| argp-ldbl.h | ||
| atomic_wide_counter.h | ||
| cmathcalls.h | ||
| cpu-set.h | ||
| dl_find_object.h | ||
| dlfcn.h | ||
| endian.h | ||
| err-ldbl.h | ||
| error-ldbl.h | ||
| error.h | ||
| fcntl2.h | ||
| getopt_core.h | ||
| getopt_ext.h | ||
| getopt_posix.h | ||
| locale.h | ||
| mathcalls-helper-functions.h | ||
| mathcalls-narrow.h | ||
| mathcalls.h | ||
| monetary-ldbl.h | ||
| mqueue2.h | ||
| poll2.h | ||
| posix1_lim.h | ||
| posix2_lim.h | ||
| printf-ldbl.h | ||
| select2.h | ||
| select-decl.h | ||
| setjmp2.h | ||
| sigstack.h | ||
| sigstksz.h | ||
| socket2.h | ||
| stab.def | ||
| statx-generic.h | ||
| statx.h | ||
| stdio2-decl.h | ||
| stdio2.h | ||
| stdio-ldbl.h | ||
| stdio.h | ||
| stdlib-float.h | ||
| stdlib-ldbl.h | ||
| stdlib.h | ||
| string2.h | ||
| string_fortified.h | ||
| strings_fortified.h | ||
| syslog-decl.h | ||
| syslog-ldbl.h | ||
| syslog.h | ||
| types.h | ||
| unistd_ext.h | ||
| unistd-decl.h | ||
| unistd.h | ||
| wchar2-decl.h | ||
| wchar2.h | ||
| wchar-ldbl.h | ||
| wctype-wchar.h | ||
| xopen_lim.h | ||