From fc6b177dee33365ccb29fe6d2092223cf8d679f9 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 5 Oct 2009 18:17:32 +0200 Subject: [PATCH] futex: Nullify robust lists after cleanup The robust list pointers of user space held futexes are kept intact over an exec() call. When the exec'ed task exits exit_robust_list() is called with the stale pointer. The risk of corruption is minimal, but still it is incorrect to keep the pointers valid. Actually glibc should uninstall the robust list before calling exec() but we have to deal with it anyway. Nullify the pointers after [compat_]exit_robust_list() has been called. Reported-by: Anirban Sinha Signed-off-by: Peter Zijlstra Signed-off-by: Thomas Gleixner LKML-Reference: Cc: stable@kernel.org --- kernel/fork.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index bfee931ee3f..88ef51ca84d 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -543,11 +543,15 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm) /* Get rid of any futexes when releasing the mm */ #ifdef CONFIG_FUTEX - if (unlikely(tsk->robust_list)) + if (unlikely(tsk->robust_list)) { exit_robust_list(tsk); + tsk->robust_list = NULL; + } #ifdef CONFIG_COMPAT - if (unlikely(tsk->compat_robust_list)) + if (unlikely(tsk->compat_robust_list)) { compat_exit_robust_list(tsk); + tsk->compat_robust_list = NULL; + } #endif #endif