linux-kernel - [PATCH] fix freeing user

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Message-ID: <AANLkTi=vfO-rs_iStXkPC7STSqfgUEW_JKt2w1=Wmf6Z@mail.gmail.com>
Date:	Thu, 23 Dec 2010 20:52:34 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH] fix freeing user_struct in user cache

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@...il.com>
---

--- 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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