fix signal masking race in pthread_create with priority attributes

[musl] / src / signal / sigaction.c

diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index f7ff4a6..6eca06f 100644 (file)
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -6,11 +6,7 @@
 #include "libc.h"
 #include "ksigaction.h"
 
-void __restore(), __restore_rt();
-
-static pthread_t dummy(void) { return 0; }
-weak_alias(dummy, __pthread_self_def);
-
+static int unmask_done;
 static unsigned long handler_set[_NSIG/(8*sizeof(long))];
 
 void __get_handler_set(sigset_t *set)
@@ -21,15 +17,24 @@ void __get_handler_set(sigset_t *set)
 int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigaction *restrict old)
 {
        struct k_sigaction ksa, ksa_old;
-       if (sig >= (unsigned)_NSIG) {
-               errno = EINVAL;
-               return -1;
-       }
        if (sa) {
                if ((uintptr_t)sa->sa_handler > 1UL) {
                        a_or_l(handler_set+(sig-1)/(8*sizeof(long)),
                                1UL<<(sig-1)%(8*sizeof(long)));
-                       __pthread_self_def();
+
+                       /* If pthread_create has not yet been called,
+                        * implementation-internal signals might not
+                        * yet have been unblocked. They must be
+                        * unblocked before any signal handler is
+                        * installed, so that an application cannot
+                        * receive an illegal sigset_t (with them
+                        * blocked) as part of the ucontext_t passed
+                        * to the signal handler. */
+                       if (!libc.threaded && !unmask_done) {
+                               __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
+                                       SIGPT_SET, 0, _NSIG/8);
+                               unmask_done = 1;
+                       }
                }
                ksa.handler = sa->sa_handler;
                ksa.flags = sa->sa_flags | SA_RESTORER;
@@ -48,7 +53,7 @@ int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigact
 
 int __sigaction(int sig, const struct sigaction *restrict sa, struct sigaction *restrict old)
 {
-       if (sig-32U < 3) {
+       if (sig-32U < 3 || sig-1U >= _NSIG-1) {
                errno = EINVAL;
                return -1;
        }