[PATCH] fix freeing user_struct in user cache

[Hillf Danton]

When racing on adding into user cache, the new allocated from mm slab
is freed without putting user namespace.

Since the user namespace is already operated by getting, putting has
to be issued.

btw, it could be freed out of lock?

Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
---

--- a/kernel/user.c	2010-11-01 19:54:12.000000000 +0800
+++ b/kernel/user.c	2010-12-23 20:42:00.000000000 +0800
@@ -158,6 +158,7 @@ struct user_struct *alloc_uid(struct use
 		spin_lock_irq(&uidhash_lock);
 		up = uid_hash_find(uid, hashent);
 		if (up) {
+			put_user_ns(ns);
 			key_put(new->uid_keyring);
 			key_put(new->session_keyring);
 			kmem_cache_free(uid_cachep, new);
--
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