From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out4-smtp.messagingengine.com ([66.111.4.28]:41305 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751734AbdJXImc (ORCPT ); Tue, 24 Oct 2017 04:42:32 -0400 Subject: FAILED: patch "[PATCH] FS-Cache: fix dereference of NULL user_key_payload" failed to apply to 4.4-stable tree To: ebiggers@google.com, dhowells@redhat.com, james.l.morris@oracle.com, stable@vger.kernel.org Cc: From: Date: Tue, 24 Oct 2017 09:57:33 +0200 Message-ID: <150883185380205@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >>From d124b2c53c7bee6569d2a2d0b18b4a1afde00134 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 9 Oct 2017 12:40:00 -0700 Subject: [PATCH] FS-Cache: fix dereference of NULL user_key_payload 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 Cc: [v2.6.32+] Signed-off-by: Eric Biggers Signed-off-by: David Howells diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c index b5ab06fabc60..0438d4cd91ef 100644 --- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -331,6 +331,13 @@ static void fscache_objlist_config(struct fscache_objlist_data *data) rcu_read_lock(); confkey = user_key_payload_rcu(key); + if (!confkey) { + /* key was revoked */ + rcu_read_unlock(); + key_put(key); + goto no_config; + } + buf = confkey-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--) {