Filter out NPTL internal signals (BZ #22391)

This patch filters out the internal NPTL signals (SIGCANCEL/SIGTIMER and
SIGSETXID) from signal functions.  GLIBC on Linux requires both signals to
proper implement pthread cancellation, posix timers, and set*id posix
thread synchronization.

And not filtering out the internal signal is troublesome:

  - A conformant program on a architecture that does not filter out the
    signals might inadvertently disable pthread asynchronous cancellation,
    set*id synchronization or posix timers.

  - It might also to security issues if SIGSETXID is masked and set*id
    functions are called (some threads might have effective user or group
    id different from the rest).

The changes are basically:

  - Change __is_internal_signal to bool and used on all signal function
    that has a signal number as input.  Also for signal function which accepts
    signals sets (sigset_t) it assumes that canonical function were used to
    add/remove signals which lead to some input simplification.

  - Fix tst-sigset.c to avoid check for SIGCANCEL/SIGTIMER and SIGSETXID.
    It is rewritten to check each signal indidually and to check realtime
    signals using canonical macros.

  - Add generic __clear_internal_signals and __is_internal_signal
    version since both symbols are used on generic implementations.

  - Remove superflous sysdeps/nptl/sigfillset.c.

  - Remove superflous SIGTIMER handling on Linux __is_internal_signal
    since it is the same of SIGCANCEL.

  - Remove dangling define and obvious comment on nptl/sigaction.c.

Checked on x86_64-linux-gnu.

	[BZ #22391]
	* nptl/sigaction.c (__sigaction): Use __is_internal_signal to
	check for internal nptl signals.
	* nptl/sigaction.c (__sigaction): Likewise.
	* signal/sigaddset.c (sigaddset): Likewise.
	* signal/sigdelset.c (sigdelset): Likewise.
	* sysdeps/posix/signal.c (__bsd_signal): Likewise.
	* sysdeps/posix/sigset.c (sigset): Call and check sigaddset return
	value.
	* signal/sigfillset.c (sigfillset): User __clear_internal_signals
	to filter out internal nptl signals.
	* signal/tst-sigset.c (do_test): Check ech signal indidually and
	also check realtime signals using standard macros.
	* sysdeps/generic/internal-signals.h (__clear_internal_signals,
	__is_internal_signal, __libc_signal_block_all,
	__libc_signal_block_app, __libc_signal_restore_set): New functions.
	* sysdeps/nptl/sigfillset.c: Remove file.
	* sysdeps/unix/sysv/linux/internal-signals.h (__is_internal_signal):
	Change return to bool.
	(__clear_internal_signals): Remove SIGTIMER clean since it is
	equal to SIGCANEL on Linux.
	* sysdeps/unix/sysv/linux/sigtimedwait.c (__sigtimedwait): Assume
	signal set was constructed using standard functions.

Reported-by: Yury Norov <ynorov@caviumnetworks.com>

2 files changed, 5 insertions, 10 deletions

diff --git a/sysdeps/posix/signal.c b/sysdeps/posix/signal.c
index a4a0875ae5..8a135c7b0e 100644
--- a/sysdeps/posix/signal.c
+++ b/sysdeps/posix/signal.c
@@ -18,8 +18,8 @@
 
 #include <errno.h>
 #include <signal.h>
-#include <string.h>	/* For the real memset prototype.  */
 #include <sigsetops.h>
+#include <internal-signals.h>
 
 sigset_t _sigintr attribute_hidden;		/* Set by siginterrupt.  */
 
@@ -31,7 +31,8 @@ __bsd_signal (int sig, __sighandler_t handler)
   struct sigaction act, oact;
 
   /* Check signal extents to protect __sigismember.  */
-  if (handler == SIG_ERR || sig < 1 || sig >= NSIG)
+  if (handler == SIG_ERR || sig < 1 || sig >= NSIG
+      || __is_internal_signal (sig))
     {
       __set_errno (EINVAL);
       return SIG_ERR;
diff --git a/sysdeps/posix/sigset.c b/sysdeps/posix/sigset.c
index b62aa3cc84..6ab4a48767 100644
--- a/sysdeps/posix/sigset.c
+++ b/sysdeps/posix/sigset.c
@@ -31,15 +31,9 @@ sigset (int sig, __sighandler_t disp)
   sigset_t set;
   sigset_t oset;
 
-  /* Check signal extents to protect __sigismember.  */
-  if (disp == SIG_ERR || sig < 1 || sig >= NSIG)
-    {
-      __set_errno (EINVAL);
-      return SIG_ERR;
-    }
-
   __sigemptyset (&set);
-  __sigaddset (&set, sig);
+  if (sigaddset (&set, sig) < 0)
+    return SIG_ERR;
 
   if (disp == SIG_HOLD)
     {