From 2f65dd475c6a8a997145ea83cc3d2d5e6dc55af1 Mon Sep 17 00:00:00 2001 From: John Wright Date: Wed, 29 Apr 2009 14:32:01 -0600 Subject: [PATCH] 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 #include 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 Cc: Andi Kleen Cc: John Wright LKML-Reference: <1241037121-14805-1-git-send-email-john.wright@hp.com> Signed-off-by: Ingo Molnar --- arch/x86/vdso/vclock_gettime.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index d9d35824c56f..6a40b78b46aa 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -104,11 +104,13 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz) { long ret; if (likely(gtod->sysctl_enabled && gtod->clock.vread)) { - BUILD_BUG_ON(offsetof(struct timeval, tv_usec) != - offsetof(struct timespec, tv_nsec) || - sizeof(*tv) != sizeof(struct timespec)); - do_realtime((struct timespec *)tv); - tv->tv_usec /= 1000; + if (likely(tv != NULL)) { + BUILD_BUG_ON(offsetof(struct timeval, tv_usec) != + offsetof(struct timespec, tv_nsec) || + sizeof(*tv) != sizeof(struct timespec)); + do_realtime((struct timespec *)tv); + tv->tv_usec /= 1000; + } if (unlikely(tz != NULL)) { /* Avoid memcpy. Some old compilers fail to inline it */ tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;