fix unintended observability of SIGABRT disposition reset via sigaction

[musl] / src / signal / sigaction.c

diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index a473740..7232d4b 100644 (file)
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -21,6 +21,13 @@ int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigact
 {
        struct k_sigaction ksa, ksa_old;
        unsigned long set[_NSIG/(8*sizeof(long))];
+       /* Doing anything with the disposition of SIGABRT requires a lock,
+        * so that it cannot be changed while abort is terminating the
+        * process and so any change made by abort can't be observed. */
+       if (sig == SIGABRT) {
+               __block_all_sigs(&set);
+               LOCK(__abort_lock);
+       }
        if (sa) {
                if ((uintptr_t)sa->sa_handler > 1UL) {
                        a_or_l(handler_set+(sig-1)/(8*sizeof(long)),
@@ -44,21 +51,13 @@ int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigact
                                a_store(&__eintr_valid_flag, 1);
                        }
                }
-               /* Changing the disposition of SIGABRT to anything but
-                * SIG_DFL requires a lock, so that it cannot be changed
-                * while abort is terminating the process after simply
-                * calling raise(SIGABRT) failed to do so. */
-               if (sa->sa_handler != SIG_DFL && sig == SIGABRT) {
-                       __block_all_sigs(&set);
-                       LOCK(__abort_lock);
-               }
                ksa.handler = sa->sa_handler;
                ksa.flags = sa->sa_flags | SA_RESTORER;
                ksa.restorer = (sa->sa_flags & SA_SIGINFO) ? __restore_rt : __restore;
                memcpy(&ksa.mask, &sa->sa_mask, _NSIG/8);
        }
        int r = __syscall(SYS_rt_sigaction, sig, sa?&ksa:0, old?&ksa_old:0, _NSIG/8);
-       if (sig == SIGABRT && sa && sa->sa_handler != SIG_DFL) {
+       if (sig == SIGABRT) {
                UNLOCK(__abort_lock);
                __restore_sigs(&set);
        }