Re: [PATCH v4 2/4] Filter out NPTL internal signals (BZ #22391)

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

If no one opposes, I will commit this shortly.

On 19/02/2018 14:50, Adhemerval Zanella wrote:
> 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
>>