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>

5 files changed, 76 insertions, 38 deletions

diff --git a/signal/sigaction.c b/signal/sigaction.c
index f761ca2..c99001a 100644
--- a/signal/sigaction.c
+++ b/signal/sigaction.c
@@ -24,7 +24,7 @@
 int
 __sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
 {
-  if (sig <= 0 || sig >= NSIG)
+  if (sig <= 0 || sig >= NSIG || __is_internal_signal (sig))
     {
       __set_errno (EINVAL);
       return -1;
diff --git a/signal/sigaddset.c b/signal/sigaddset.c
index d310890..7238df4 100644
--- a/signal/sigaddset.c
+++ b/signal/sigaddset.c
@@ -17,13 +17,14 @@
 
 #include <errno.h>
 #include <signal.h>
-#include <sigsetops.h>
+#include <internal-signals.h>
 
 /* Add SIGNO to SET.  */
 int
 sigaddset (sigset_t *set, int signo)
 {
-  if (set == NULL || signo <= 0 || signo >= NSIG)
+  if (set == NULL || signo <= 0 || signo >= NSIG
+      || __is_internal_signal (signo))
     {
       __set_errno (EINVAL);
       return -1;
diff --git a/signal/sigdelset.c b/signal/sigdelset.c
index cd83dda..011978c 100644
--- a/signal/sigdelset.c
+++ b/signal/sigdelset.c
@@ -17,13 +17,14 @@
 
 #include <errno.h>
 #include <signal.h>
-#include <sigsetops.h>
+#include <internal-signals.h>
 
 /* Add SIGNO to SET.  */
 int
 sigdelset (sigset_t *set, int signo)
 {
-  if (set == NULL || signo <= 0 || signo >= NSIG)
+  if (set == NULL || signo <= 0 || signo >= NSIG
+      || __is_internal_signal (signo))
     {
       __set_errno (EINVAL);
       return -1;
diff --git a/signal/sigfillset.c b/signal/sigfillset.c
index e586fd9..83dd583 100644
--- a/signal/sigfillset.c
+++ b/signal/sigfillset.c
@@ -18,6 +18,7 @@
 #include <errno.h>
 #include <signal.h>
 #include <string.h>
+#include <internal-signals.h>
 
 /* Set all signals in SET.  */
 int
@@ -31,14 +32,7 @@ sigfillset (sigset_t *set)
 
   memset (set, 0xff, sizeof (sigset_t));
 
-  /* If the implementation uses a cancellation signal don't set the bit.  */
-#ifdef SIGCANCEL
-  __sigdelset (set, SIGCANCEL);
-#endif
-  /* Likewise for the signal to implement setxid.  */
-#ifdef SIGSETXID
-  __sigdelset (set, SIGSETXID);
-#endif
+  __clear_internal_signals (set);
 
   return 0;
 }
diff --git a/signal/tst-sigset.c b/signal/tst-sigset.c
index d47adcc..a2b764d 100644
--- a/signal/tst-sigset.c
+++ b/signal/tst-sigset.c
@@ -1,43 +1,85 @@
 /* Test sig*set functions.  */
 
 #include <signal.h>
-#include <stdio.h>
 
-#define TEST_FUNCTION do_test ()
+#include <support/check.h>
+
 static int
 do_test (void)
 {
-  int result = 0;
-  int sig = -1;
+  sigset_t set;
+  TEST_VERIFY (sigemptyset (&set) == 0);
 
-#define TRY(call)							      \
-  if (call)								      \
-    {									      \
-      printf ("%s (sig = %d): %m\n", #call, sig);			      \
-      result = 1;							      \
-    }									      \
-  else
+#define VERIFY(set, sig)			\
+  TEST_VERIFY (sigismember (&set, sig) == 0);	\
+  TEST_VERIFY (sigaddset (&set, sig) == 0);	\
+  TEST_VERIFY (sigismember (&set, sig) != 0);	\
+  TEST_VERIFY (sigdelset (&set, sig) == 0);	\
+  TEST_VERIFY (sigismember (&set, sig) == 0)
 
+  /* ISO C99 signals.  */
+  VERIFY (set, SIGINT);
+  VERIFY (set, SIGILL);
+  VERIFY (set, SIGABRT);
+  VERIFY (set, SIGFPE);
+  VERIFY (set, SIGSEGV);
+  VERIFY (set, SIGTERM);
 
-  sigset_t set;
-  TRY (sigemptyset (&set) != 0);
+  /* Historical signals specified by POSIX. */
+  VERIFY (set, SIGHUP);
+  VERIFY (set, SIGQUIT);
+  VERIFY (set, SIGTRAP);
+  VERIFY (set, SIGKILL);
+  VERIFY (set, SIGBUS);
+  VERIFY (set, SIGSYS);
+  VERIFY (set, SIGPIPE);
+  VERIFY (set, SIGALRM);
+
+  /* New(er) POSIX signals (1003.1-2008, 1003.1-2013).  */
+  VERIFY (set, SIGURG);
+  VERIFY (set, SIGSTOP);
+  VERIFY (set, SIGTSTP);
+  VERIFY (set, SIGCONT);
+  VERIFY (set, SIGCHLD);
+  VERIFY (set, SIGTTIN);
+  VERIFY (set, SIGTTOU);
+  VERIFY (set, SIGPOLL);
+  VERIFY (set, SIGXCPU);
+  VERIFY (set, SIGXFSZ);
+  VERIFY (set, SIGVTALRM);
+  VERIFY (set, SIGPROF);
+  VERIFY (set, SIGUSR1);
+  VERIFY (set, SIGUSR2);
+
+  /* Nonstandard signals found in all modern POSIX systems
+     (including both BSD and Linux).  */
+  VERIFY (set, SIGWINCH);
 
-#ifdef SIGRTMAX
-  int max_sig = SIGRTMAX;
-#else
-  int max_sig = NSIG - 1;
+  /* Arch-specific signals.  */
+#ifdef SIGEMT
+  VERIFY (set, SIGEMT);
+#endif
+#ifdef SIGLOST
+  VERIFY (set, SIGLOST);
+#endif
+#ifdef SIGINFO
+  VERIFY (set, SIGINFO);
+#endif
+#ifdef SIGSTKFLT
+  VERIFY (set, SIGSTKFLT);
+#endif
+#ifdef SIGPWR
+  VERIFY (set, SIGPWR);
 #endif
 
-  for (sig = 1; sig <= max_sig; ++sig)
+  /* Read-time signals (POSIX.1b real-time extensions).  If they are
+     supported SIGRTMAX value is greater than SIGRTMIN.  */
+  for (int rtsig = SIGRTMIN; rtsig <= SIGRTMAX; rtsig++)
     {
-      TRY (sigismember (&set, sig) != 0);
-      TRY (sigaddset (&set, sig) != 0);
-      TRY (sigismember (&set, sig) == 0);
-      TRY (sigdelset (&set, sig) != 0);
-      TRY (sigismember (&set, sig) != 0);
+      VERIFY (set, rtsig);
     }
 
-  return result;
+  return 0;
 }
 
-#include "../test-skeleton.c"
+#include <support/test-driver.c>