block all signals during rsyscall

otherwise a signal handler could see an inconsistent and nonconformant
program state where different threads have different uids/gids.

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 344b39f8d2031694132d88142f0a1786b8b401bc..cdf36ff249063bbd6b053ec7247afae3adf29e13 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -85,7 +85,7 @@ static void rsyscall_handler(int sig, siginfo_t *si, void *ctx)
        /* Threads which have already decremented themselves from the
         * thread count must not increment rs.cnt or otherwise act. */
        if (self->dead) {
-               sigaddset(&((ucontext_t *)ctx)->uc_sigmask, SIGSYSCALL);
+               sigfillset(&((ucontext_t *)ctx)->uc_sigmask);
                return;
        }
 
@@ -151,13 +151,18 @@ static void init_threads()
        libc.lockfile = __lockfile;
        libc.cancelpt = cancelpt;
        libc.rsyscall = rsyscall;
+
+       sigfillset(&sa.sa_mask);
+       sa.sa_sigaction = rsyscall_handler;
+       __libc_sigaction(SIGSYSCALL, &sa, 0);
+
+       sigemptyset(&sa.sa_mask);
        sa.sa_sigaction = cancel_handler;
        __libc_sigaction(SIGCANCEL, &sa, 0);
+
        sigaddset(&sa.sa_mask, SIGSYSCALL);
        sigaddset(&sa.sa_mask, SIGCANCEL);
-       sa.sa_sigaction = rsyscall_handler;
-       __libc_sigaction(SIGSYSCALL, &sa, 0);
-       sigprocmask(SIG_UNBLOCK, &sa.sa_mask, 0);
+       __libc_sigprocmask(SIG_UNBLOCK, &sa.sa_mask, 0);
 }
 
 static int start(void *p)