signal: Only handle on NSIG signals on signal functions (BZ #25657)

The upper bits of the sigset_t s not fully initialized in the signal
mask calls that return information from kernel (sigprocmask,
sigpending, and pthread_sigmask), since the exported sigset_t size
(1024 bits) is larger than Linux support one (64 or 128 bits).
It might make sigisemptyset/sigorset/sigandset fail if the mask
is filled prior the call.

This patch changes the internal signal function to handle up to
supported Linux signal number (_NSIG), the remaining bits are
untouched.

Checked on x86_64-linux-gnu and i686-linux-gnu.

3 files changed, 66 insertions, 5 deletions

diff --git a/nptl/Makefile b/nptl/Makefile
index 4816fa254e..33fa03807e 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -293,7 +293,7 @@ tests = tst-attr2 tst-attr3 tst-default-attr \
 	tst-cleanup0 tst-cleanup1 tst-cleanup2 tst-cleanup3 tst-cleanup4 \
 	tst-flock1 tst-flock2 \
 	tst-signal1 tst-signal2 tst-signal3 tst-signal4 tst-signal5 \
-	tst-signal6 \
+	tst-signal6 tst-signal8 \
 	tst-exec1 tst-exec2 tst-exec3 tst-exec4 tst-exec5 \
 	tst-exit1 tst-exit2 tst-exit3 \
 	tst-stdio1 tst-stdio2 \
diff --git a/nptl/pthread_sigmask.c b/nptl/pthread_sigmask.c
index c6c6e83c08..d266d296c5 100644
--- a/nptl/pthread_sigmask.c
+++ b/nptl/pthread_sigmask.c
@@ -29,12 +29,11 @@ __pthread_sigmask (int how, const sigset_t *newmask, sigset_t *oldmask)
   /* The only thing we have to make sure here is that SIGCANCEL and
      SIGSETXID is not blocked.  */
   if (newmask != NULL
-      && (__builtin_expect (__sigismember (newmask, SIGCANCEL), 0)
-	  || __builtin_expect (__sigismember (newmask, SIGSETXID), 0)))
+      && (__glibc_unlikely (__sigismember (newmask, SIGCANCEL))
+         || __glibc_unlikely (__sigismember (newmask, SIGSETXID))))
     {
       local_newmask = *newmask;
-      __sigdelset (&local_newmask, SIGCANCEL);
-      __sigdelset (&local_newmask, SIGSETXID);
+      __clear_internal_signals (&local_newmask);
       newmask = &local_newmask;
     }
 
diff --git a/nptl/tst-signal8.c b/nptl/tst-signal8.c
new file mode 100644
index 0000000000..9da7e5ef07
--- /dev/null
+++ b/nptl/tst-signal8.c
@@ -0,0 +1,62 @@
+/* Tests for sigisemptyset and pthread_sigmask.
+   Copyright (C) 2020 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/>.  */
+
+#include <signal.h>
+
+#include <support/check.h>
+#include <support/xthread.h>
+
+static void *
+tf (void *arg)
+{
+  {
+    sigset_t set;
+    sigemptyset (&set);
+    TEST_COMPARE (pthread_sigmask (SIG_BLOCK, 0, &set), 0);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  {
+    sigset_t set;
+    sigfillset (&set);
+    TEST_COMPARE (pthread_sigmask (SIG_BLOCK, 0, &set), 0);
+    TEST_COMPARE (sigisemptyset (&set), 1);
+  }
+
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  /* Ensure current SIG_BLOCK mask empty.  */
+  {
+    sigset_t set;
+    sigemptyset (&set);
+    TEST_COMPARE (sigprocmask (SIG_BLOCK, &set, 0), 0);
+  }
+
+  {
+    pthread_t thr = xpthread_create (NULL, tf, NULL);
+    xpthread_join (thr);
+  }
+
+  return 0;
+}
+
+#include <support/test-driver.c>