Patchwork [v4,2/4] Filter out NPTL internal signals (BZ #22391)

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Submitter Adhemerval Zanella Netto
Date Feb. 12, 2018, 12:42 p.m.
Message ID <1518439345-6013-2-git-send-email-adhemerval.zanella@linaro.org>
Download mbox | patch
Permalink /patch/25912/
State New
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Comments

Adhemerval Zanella Netto - Feb. 12, 2018, 12:42 p.m.
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.
	* 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/nptl/nptl-signals.h (__clear_internal_signals,
	__is_internal_signal): New functions.
	* sysdeps/nptl/sigfillset.c: Remove file.
	* sysdeps/unix/sysv/linux/nptl-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.
	* sysdeps/unix/sysv/linux/sigwait.c (do_sigtwait): Likewise.

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reported-by: Yury Norov <ynorov@caviumnetworks.com>
---
 ChangeLog                                  | 23 ++++++++
 nptl/sigaction.c                           | 14 +----
 signal/sigaction.c                         |  2 +-
 signal/sigaddset.c                         |  5 +-
 signal/sigdelset.c                         |  5 +-
 signal/sigfillset.c                        | 10 +---
 signal/tst-sigset.c                        | 92 ++++++++++++++++++++++--------
 sysdeps/generic/internal-signals.h         | 11 ++++
 sysdeps/nptl/sigfillset.c                  | 20 -------
 sysdeps/posix/signal.c                     |  5 +-
 sysdeps/posix/sigset.c                     | 10 +---
 sysdeps/unix/sysv/linux/internal-signals.h |  4 +-
 sysdeps/unix/sysv/linux/sigtimedwait.c     | 17 +-----
 13 files changed, 122 insertions(+), 96 deletions(-)
 delete mode 100644 sysdeps/nptl/sigfillset.c
Adhemerval Zanella Netto - Feb. 19, 2018, 5:50 p.m.
Ping.

On 12/02/2018 10:42, Adhemerval Zanella wrote:
> 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.
> 	* 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/nptl/nptl-signals.h (__clear_internal_signals,
> 	__is_internal_signal): New functions.
> 	* sysdeps/nptl/sigfillset.c: Remove file.
> 	* sysdeps/unix/sysv/linux/nptl-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.
> 	* sysdeps/unix/sysv/linux/sigwait.c (do_sigtwait): Likewise.
> 
> Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> Reported-by: Yury Norov <ynorov@caviumnetworks.com>
> ---
>  ChangeLog                                  | 23 ++++++++
>  nptl/sigaction.c                           | 14 +----
>  signal/sigaction.c                         |  2 +-
>  signal/sigaddset.c                         |  5 +-
>  signal/sigdelset.c                         |  5 +-
>  signal/sigfillset.c                        | 10 +---
>  signal/tst-sigset.c                        | 92 ++++++++++++++++++++++--------
>  sysdeps/generic/internal-signals.h         | 11 ++++
>  sysdeps/nptl/sigfillset.c                  | 20 -------
>  sysdeps/posix/signal.c                     |  5 +-
>  sysdeps/posix/sigset.c                     | 10 +---
>  sysdeps/unix/sysv/linux/internal-signals.h |  4 +-
>  sysdeps/unix/sysv/linux/sigtimedwait.c     | 17 +-----
>  13 files changed, 122 insertions(+), 96 deletions(-)
>  delete mode 100644 sysdeps/nptl/sigfillset.c
> 
> diff --git a/nptl/sigaction.c b/nptl/sigaction.c
> index ddf6f5e..79b6fdc 100644
> --- a/nptl/sigaction.c
> +++ b/nptl/sigaction.c
> @@ -16,22 +16,12 @@
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
>  
> -
> -/* This is no complete implementation.  The file is meant to be
> -   included in the real implementation to provide the wrapper around
> -   __libc_sigaction.  */
> -
> -#include <nptl/pthreadP.h>
> -
> -/* We use the libc implementation but we tell it to not allow
> -   SIGCANCEL or SIGTIMER to be handled.  */
> -#define LIBC_SIGACTION	1
> -
> +#include <internal-signals.h>
>  
>  int
>  __sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
>  {
> -  if (__glibc_unlikely (sig == SIGCANCEL || sig == SIGSETXID))
> +  if (sig <= 0 || sig >= NSIG || __is_internal_signal (sig))
>      {
>        __set_errno (EINVAL);
>        return -1;
> 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>
> diff --git a/sysdeps/generic/internal-signals.h b/sysdeps/generic/internal-signals.h
> index 01e5b75..ab0b22e 100644
> --- a/sysdeps/generic/internal-signals.h
> +++ b/sysdeps/generic/internal-signals.h
> @@ -15,3 +15,14 @@
>     You should have received a copy of the GNU Lesser General Public
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
> +
> +static inline void
> +__clear_internal_signals (sigset_t *set)
> +{
> +}
> +
> +static inline bool
> +__is_internal_signal (int sig)
> +{
> +  return false;
> +}
> diff --git a/sysdeps/nptl/sigfillset.c b/sysdeps/nptl/sigfillset.c
> deleted file mode 100644
> index 94a7680..0000000
> --- a/sysdeps/nptl/sigfillset.c
> +++ /dev/null
> @@ -1,20 +0,0 @@
> -/* Copyright (C) 2003-2018 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
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#include <nptl/pthreadP.h>
> -
> -#include <signal/sigfillset.c>
> diff --git a/sysdeps/posix/signal.c b/sysdeps/posix/signal.c
> index a4a0875..8a135c7 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 b62aa3c..6ab4a48 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)
>      {
> diff --git a/sysdeps/unix/sysv/linux/internal-signals.h b/sysdeps/unix/sysv/linux/internal-signals.h
> index e007372..5ff4cf8 100644
> --- a/sysdeps/unix/sysv/linux/internal-signals.h
> +++ b/sysdeps/unix/sysv/linux/internal-signals.h
> @@ -21,6 +21,8 @@
>  
>  #include <signal.h>
>  #include <sigsetops.h>
> +#include <stdbool.h>
> +#include <sysdep.h>
>  
>  /* The signal used for asynchronous cancelation.  */
>  #define SIGCANCEL       __SIGRTMIN
> @@ -37,7 +39,7 @@
>  
>  
>  /* Return is sig is used internally.  */
> -static inline int
> +static inline bool
>  __is_internal_signal (int sig)
>  {
>    return (sig == SIGCANCEL) || (sig == SIGSETXID);
> diff --git a/sysdeps/unix/sysv/linux/sigtimedwait.c b/sysdeps/unix/sysv/linux/sigtimedwait.c
> index 051a285..b4de885 100644
> --- a/sysdeps/unix/sysv/linux/sigtimedwait.c
> +++ b/sysdeps/unix/sysv/linux/sigtimedwait.c
> @@ -24,21 +24,8 @@ int
>  __sigtimedwait (const sigset_t *set, siginfo_t *info,
>  		const struct timespec *timeout)
>  {
> -  sigset_t tmpset;
> -  if (set != NULL
> -      && (__builtin_expect (__sigismember (set, SIGCANCEL), 0)
> -	  || __builtin_expect (__sigismember (set, SIGSETXID), 0)))
> -    {
> -      /* Create a temporary mask without the bit for SIGCANCEL set.  */
> -      // We are not copying more than we have to.
> -      memcpy (&tmpset, set, _NSIG / 8);
> -      __sigdelset (&tmpset, SIGCANCEL);
> -      __sigdelset (&tmpset, SIGSETXID);
> -      set = &tmpset;
> -    }
> -
> -    /* XXX The size argument hopefully will have to be changed to the
> -       real size of the user-level sigset_t.  */
> +  /* XXX The size argument hopefully will have to be changed to the
> +     real size of the user-level sigset_t.  */
>    int result = SYSCALL_CANCEL (rt_sigtimedwait, set, info, timeout, _NSIG / 8);
>  
>    /* The kernel generates a SI_TKILL code in si_code in case tkill is
>

Patch

diff --git a/nptl/sigaction.c b/nptl/sigaction.c
index ddf6f5e..79b6fdc 100644
--- a/nptl/sigaction.c
+++ b/nptl/sigaction.c
@@ -16,22 +16,12 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-
-/* This is no complete implementation.  The file is meant to be
-   included in the real implementation to provide the wrapper around
-   __libc_sigaction.  */
-
-#include <nptl/pthreadP.h>
-
-/* We use the libc implementation but we tell it to not allow
-   SIGCANCEL or SIGTIMER to be handled.  */
-#define LIBC_SIGACTION	1
-
+#include <internal-signals.h>
 
 int
 __sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
 {
-  if (__glibc_unlikely (sig == SIGCANCEL || sig == SIGSETXID))
+  if (sig <= 0 || sig >= NSIG || __is_internal_signal (sig))
     {
       __set_errno (EINVAL);
       return -1;
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>
diff --git a/sysdeps/generic/internal-signals.h b/sysdeps/generic/internal-signals.h
index 01e5b75..ab0b22e 100644
--- a/sysdeps/generic/internal-signals.h
+++ b/sysdeps/generic/internal-signals.h
@@ -15,3 +15,14 @@ 
    You should have received a copy of the GNU Lesser General Public
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
+
+static inline void
+__clear_internal_signals (sigset_t *set)
+{
+}
+
+static inline bool
+__is_internal_signal (int sig)
+{
+  return false;
+}
diff --git a/sysdeps/nptl/sigfillset.c b/sysdeps/nptl/sigfillset.c
deleted file mode 100644
index 94a7680..0000000
--- a/sysdeps/nptl/sigfillset.c
+++ /dev/null
@@ -1,20 +0,0 @@ 
-/* Copyright (C) 2003-2018 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
-   <http://www.gnu.org/licenses/>.  */
-
-#include <nptl/pthreadP.h>
-
-#include <signal/sigfillset.c>
diff --git a/sysdeps/posix/signal.c b/sysdeps/posix/signal.c
index a4a0875..8a135c7 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 b62aa3c..6ab4a48 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)
     {
diff --git a/sysdeps/unix/sysv/linux/internal-signals.h b/sysdeps/unix/sysv/linux/internal-signals.h
index e007372..5ff4cf8 100644
--- a/sysdeps/unix/sysv/linux/internal-signals.h
+++ b/sysdeps/unix/sysv/linux/internal-signals.h
@@ -21,6 +21,8 @@ 
 
 #include <signal.h>
 #include <sigsetops.h>
+#include <stdbool.h>
+#include <sysdep.h>
 
 /* The signal used for asynchronous cancelation.  */
 #define SIGCANCEL       __SIGRTMIN
@@ -37,7 +39,7 @@ 
 
 
 /* Return is sig is used internally.  */
-static inline int
+static inline bool
 __is_internal_signal (int sig)
 {
   return (sig == SIGCANCEL) || (sig == SIGSETXID);
diff --git a/sysdeps/unix/sysv/linux/sigtimedwait.c b/sysdeps/unix/sysv/linux/sigtimedwait.c
index 051a285..b4de885 100644
--- a/sysdeps/unix/sysv/linux/sigtimedwait.c
+++ b/sysdeps/unix/sysv/linux/sigtimedwait.c
@@ -24,21 +24,8 @@  int
 __sigtimedwait (const sigset_t *set, siginfo_t *info,
 		const struct timespec *timeout)
 {
-  sigset_t tmpset;
-  if (set != NULL
-      && (__builtin_expect (__sigismember (set, SIGCANCEL), 0)
-	  || __builtin_expect (__sigismember (set, SIGSETXID), 0)))
-    {
-      /* Create a temporary mask without the bit for SIGCANCEL set.  */
-      // We are not copying more than we have to.
-      memcpy (&tmpset, set, _NSIG / 8);
-      __sigdelset (&tmpset, SIGCANCEL);
-      __sigdelset (&tmpset, SIGSETXID);
-      set = &tmpset;
-    }
-
-    /* XXX The size argument hopefully will have to be changed to the
-       real size of the user-level sigset_t.  */
+  /* XXX The size argument hopefully will have to be changed to the
+     real size of the user-level sigset_t.  */
   int result = SYSCALL_CANCEL (rt_sigtimedwait, set, info, timeout, _NSIG / 8);
 
   /* The kernel generates a SI_TKILL code in si_code in case tkill is