From 28f300d23674fa01ae747c66ce861d4ee6aebe8c Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Tue, 18 Sep 2007 22:46:45 -0700 Subject: Fix user namespace exiting OOPs It turned out, that the user namespace is released during the do_exit() in exit_task_namespaces(), but the struct user_struct is released only during the put_task_struct(), i.e. MUCH later. On debug kernels with poisoned slabs this will cause the oops in uid_hash_remove() because the head of the chain, which resides inside the struct user_namespace, will be already freed and poisoned. Since the uid hash itself is required only when someone can search it, i.e. when the namespace is alive, we can safely unhash all the user_struct-s from it during the namespace exiting. The subsequent free_uid() will complete the user_struct destruction. For example simple program #include char stack[2 * 1024 * 1024]; int f(void *foo) { return 0; } int main(void) { clone(f, stack + 1 * 1024 * 1024, 0x10000000, 0); return 0; } run on kernel with CONFIG_USER_NS turned on will oops the kernel immediately. This was spotted during OpenVZ kernel testing. Signed-off-by: Pavel Emelyanov Signed-off-by: Alexey Dobriyan Acked-by: "Serge E. Hallyn" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 6239bc2c2baa..5445eaec6908 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1472,6 +1472,7 @@ static inline struct user_struct *get_uid(struct user_struct *u) } extern void free_uid(struct user_struct *); extern void switch_uid(struct user_struct *); +extern void release_uids(struct user_namespace *ns); #include -- cgit v1.2.3