From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761559AbZCaRoV (ORCPT ); Tue, 31 Mar 2009 13:44:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754666AbZCaRoL (ORCPT ); Tue, 31 Mar 2009 13:44:11 -0400 Received: from mx2.redhat.com ([66.187.237.31]:38479 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751905AbZCaRoK (ORCPT ); Tue, 31 Mar 2009 13:44:10 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20090331084546.6b24d66e@tleilax.poochiereds.net> References: <20090331084546.6b24d66e@tleilax.poochiereds.net> To: Jeff Layton Cc: dhowells@redhat.com, linux-kernel@vger.kernel.org, linux-cifs-client@lists.samba.org Subject: Re: consistent oops from request_key in 2.6.29 Date: Tue, 31 Mar 2009 18:44:05 +0100 Message-ID: <14730.1238521445@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org How about the attached patch? David --- From: David Howells Subject: [PATCH] KEYS: Handle there being no fallback destination keyring for request_key() When request_key() is called, without there being any standard process keyrings on which to fall back if a destination keyring is not specified, an oops is liable to occur when construct_alloc_key() calls down_write() on dest_keyring's semaphore. Due to function inlining this may be seen as an oops in down_write() as called from request_key_and_link(). This situation crops up during boot, where request_key() is called from within the kernel (such as in CIFS mounts) where nobody is actually logged in, and so PAM has not had a chance to create a session keyring and user keyrings to act as the fallback. To fix this, make construct_alloc_key() not attempt to cache a key if there is no fallback key if no destination keyring is given specifically. Signed-off-by: David Howells --- security/keys/request_key.c | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-) diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 22a3158..03fe63e 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -311,7 +311,8 @@ static int construct_alloc_key(struct key_type *type, set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags); - down_write(&dest_keyring->sem); + if (dest_keyring) + down_write(&dest_keyring->sem); /* attach the key to the destination keyring under lock, but we do need * to do another check just in case someone beat us to it whilst we @@ -322,10 +323,12 @@ static int construct_alloc_key(struct key_type *type, if (!IS_ERR(key_ref)) goto key_already_present; - __key_link(dest_keyring, key); + if (dest_keyring) + __key_link(dest_keyring, key); mutex_unlock(&key_construction_mutex); - up_write(&dest_keyring->sem); + if (dest_keyring) + up_write(&dest_keyring->sem); mutex_unlock(&user->cons_lock); *_key = key; kleave(" = 0 [%d]", key_serial(key));