From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f65.google.com ([209.85.214.65]:54258 "EHLO mail-it0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751576AbdJXXnx (ORCPT ); Tue, 24 Oct 2017 19:43:53 -0400 Received: by mail-it0-f65.google.com with SMTP id n195so12058046itg.2 for ; Tue, 24 Oct 2017 16:43:53 -0700 (PDT) From: Eric Biggers To: stable@vger.kernel.org Cc: Eric Biggers , David Howells Subject: [PATCH] FS-Cache: fix dereference of NULL user_key_payload Date: Tue, 24 Oct 2017 16:43:20 -0700 Message-Id: <20171024234320.77832-1-ebiggers3@gmail.com> Sender: stable-owner@vger.kernel.org List-ID: From: Eric Biggers commit d124b2c53c7bee6569d2a2d0b18b4a1afde00134 upstream. Please apply to stable for 4.4 through 4.10. 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 --- fs/fscache/object-list.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c index 5d5ddaa84b21..37e0c31d284f 100644 --- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -330,6 +330,13 @@ static void fscache_objlist_config(struct fscache_objlist_data *data) rcu_read_lock(); confkey = user_key_payload(key); + if (!confkey) { + /* key was revoked */ + rcu_read_unlock(); + key_put(key); + goto no_config; + } + buf = confkey-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--) { -- 2.15.0.rc0.271.g36b669edcc-goog