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Date: Mon, 29 Dec 2014 09:39:01 -0500 From: Sasha Levin <sasha.levin@...cle.com> To: linux-kernel@...r.kernel.org Cc: Sasha Levin <sasha.levin@...cle.com>, David Howells <dhowells@...hat.com>, James Morris <james.l.morris@...cle.com>, "Serge E. Hallyn" <serge@...lyn.com>, keyrings@...ux-nfs.org (open list:KEYS/KEYRINGS:), linux-security-module@...r.kernel.org (open list:SECURITY SUBSYSTEM) Subject: [PATCH] KEYS: close race between key lookup and freeing When a key is being garbage collected, it's key->user would get put before the ->destroy() callback is called, where the key is removed from it's respective tracking structures. This leaves a key hanging in a semi-invalid state which leaves a window open for a different task to try an access key->user. An example is find_keyring_by_name() which would dereference key->user for a key that is in the process of being garbage collected (where key->user was freed but ->destroy() wasn't called yet - so it's still present in the linked list). This would cause either a panic, or corrupt memory. Signed-off-by: Sasha Levin <sasha.levin@...cle.com> --- security/keys/gc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/keys/gc.c b/security/keys/gc.c index 9609a7f..c795237 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -148,12 +148,12 @@ static noinline void key_gc_unused_keys(struct list_head *keys) if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) atomic_dec(&key->user->nikeys); - key_user_put(key->user); - /* now throw away the key memory */ if (key->type->destroy) key->type->destroy(key); + key_user_put(key->user); + kfree(key->description); #ifdef KEY_DEBUGGING -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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