nptl: Do not set signal mask on second setjmp return [BZ #28607]

__libc_signal_restore_set was in the wrong place: It also ran
when setjmp returned the second time (after pthread_exit or
pthread_cancel).  This is observable with blocked pending
signals during thread exit.

Fixes commit b3cae39dcbfa2432b3f3aa28854d8ac57f0de1b8
("nptl: Start new threads with all signals blocked [BZ #25098]").

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index d6ea43a75454f443f59d3e83775cf5fdb1d2eff6..bad9eeb52fcd9e17dc7569371298ba66d4cddc1a 100644 (file)
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -406,8 +406,6 @@ start_thread (void *arg)
   unwind_buf.priv.data.prev = NULL;
   unwind_buf.priv.data.cleanup = NULL;
 
-  __libc_signal_restore_set (&pd->sigmask);
-
   /* Allow setxid from now onwards.  */
   if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0) == -2))
     futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
@@ -417,6 +415,8 @@ start_thread (void *arg)
       /* Store the new cleanup handler info.  */
       THREAD_SETMEM (pd, cleanup_jmp_buf, &unwind_buf);
 
+      __libc_signal_restore_set (&pd->sigmask);
+
       LIBC_PROBE (pthread_start, 3, (pthread_t) pd, pd->start_routine, pd->arg);
 
       /* Run the code the user provided.  */

diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile
index df8943f4860a39d8667edde206d68ab68d292541..c65710169697ad958b1b76219563f1c37b64c2bb 100644 (file)
--- a/sysdeps/pthread/Makefile
+++ b/sysdeps/pthread/Makefile
@@ -118,6 +118,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
         tst-unload \
         tst-unwind-thread \
         tst-pt-vfork1 tst-pt-vfork2 tst-vfork1x tst-vfork2x \
+        tst-pthread-exit-signal \
         tst-pthread-setuid-loop \
         tst-pthread_cancel-exited \
         tst-pthread_cancel-select-loop \

diff --git a/sysdeps/pthread/tst-pthread-exit-signal.c b/sysdeps/pthread/tst-pthread-exit-signal.c
new file mode 100644 (file)
index 0000000..b4526fe
--- /dev/null
+++ b/sysdeps/pthread/tst-pthread-exit-signal.c
@@ -0,0 +1,45 @@
+/* Test that pending signals are not delivered on thread exit (bug 28607).
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Due to bug 28607, pthread_kill (or pthread_cancel) restored the
+   signal mask during during thread exit, triggering the delivery of a
+   blocked pending signal (SIGUSR1 in this test).  */
+
+#include <support/xthread.h>
+#include <support/xsignal.h>
+
+static void *
+threadfunc (void *closure)
+{
+  sigset_t sigmask;
+  sigfillset (&sigmask);
+  xpthread_sigmask (SIG_SETMASK, &sigmask, NULL);
+  xpthread_kill (pthread_self (), SIGUSR1);
+  pthread_exit (NULL);
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  pthread_t thr = xpthread_create (NULL, threadfunc, NULL);
+  xpthread_join (thr);
+  return 0;
+}
+
+#include <support/test-driver.c>