Commit 2f65dd47 authored Apr 29, 2009 by John Wright Committed by Ingo Molnar Apr 30, 2009

x86: gettimeofday() vDSO: fix segfault when tv == NULL

According to the gettimeofday(2) manual:

       If either tv or tz is NULL, the corresponding structure is not
       set or returned.

Since it is legal to give NULL as the tv argument, the code should make
sure tv is not NULL before trying to dereference it.

This issue manifests itself on x86_64 when vdso=0 is not on the kernel
command-line and libc uses the vDSO for gettimeofday() (e.g. glibc >=
2.7).  A simple reproducer:

  #include <stdio.h>
  #include <sys/time.h>

  int main(void)
  {
      struct timezone tz;

      gettimeofday(NULL, &tz);

      return 0;
  }

See http://bugs.debian.org/466491

 for more details.

[ Impact: fix gettimeofday(NULL, &tz) segfault ]

Signed-off-by: John Wright <john.wright@hp.com>
Cc: Andi Kleen <ak@suse.de>
Cc: John Wright <john.wright@hp.com>
LKML-Reference: <1241037121-14805-1-git-send-email-john.wright@hp.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 091438dd

arch/x86/vdso/vclock_gettime.c

+7 −5

Original line number	Original line	Diff line number	Diff line
	@@ -104,11 +104,13 @@ notrace int __vdso_gettimeofday(struct timeval tv, struct timezone tz)
	{		{
	long ret;		long ret;
	if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {		if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
			if (likely(tv != NULL)) {
	BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=		BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
	offsetof(struct timespec, tv_nsec) \|\|		offsetof(struct timespec, tv_nsec) \|\|
	sizeof(*tv) != sizeof(struct timespec));		sizeof(*tv) != sizeof(struct timespec));
	do_realtime((struct timespec *)tv);		do_realtime((struct timespec *)tv);
	tv->tv_usec /= 1000;		tv->tv_usec /= 1000;
			}
	if (unlikely(tz != NULL)) {		if (unlikely(tz != NULL)) {
	/* Avoid memcpy. Some old compilers fail to inline it */		/* Avoid memcpy. Some old compilers fail to inline it */
	tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;		tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;