From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:40548 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933384AbdJXNPf (ORCPT ); Tue, 24 Oct 2017 09:15:35 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, James Morris , Eric Biggers , David Howells Subject: [PATCH 4.13 63/85] FS-Cache: fix dereference of NULL user_key_payload Date: Tue, 24 Oct 2017 15:07:37 +0200 Message-Id: <20171024125656.531871288@linuxfoundation.org> In-Reply-To: <20171024125654.028122623@linuxfoundation.org> References: <20171024125654.028122623@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit d124b2c53c7bee6569d2a2d0b18b4a1afde00134 upstream. When the file /proc/fs/fscache/objects (available with CONFIG_FSCACHE_OBJECT_LIST=y) is opened, we request a user key with description "fscache:objlist", then access its payload. However, a revoked key has a NULL payload, and we failed to check for this. request_key() *does* skip revoked keys, but there is still a window where the key can be revoked before we access its payload. Fix it by checking for a NULL payload, treating it like a key which was already revoked at the time it was requested. Fixes: 4fbf4291aa15 ("FS-Cache: Allow the current state of all objects to be dumped") Reviewed-by: James Morris Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: Greg Kroah-Hartman --- fs/fscache/object-list.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -330,6 +330,13 @@ static void fscache_objlist_config(struc rcu_read_lock(); confkey = user_key_payload_rcu(key); + if (!confkey) { + /* key was revoked */ + rcu_read_unlock(); + key_put(key); + goto no_config; + } + buf = confkey->data; for (len = confkey->datalen - 1; len >= 0; len--) {