From: Eric Biggers Date: Mon, 09 Oct 2017 19:40:00 +0000 Subject: [PATCH v2] FS-Cache: fix dereference of NULL user_key_payload Message-Id: <20171009194000.66958-1-ebiggers3@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: To: linux-security-module@vger.kernel.org From: Eric Biggers 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 --- Changed since v1: added Reviewed-by and resent as standalone patch. Can this please be taken through the keyrings tree? 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 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fscache_objlist_data *data) rcu_read_lock(); confkey = user_key_payload_rcu(key); + if (!confkey) { + /* key was revoked */ + rcu_read_unlock(); + key_put(key); + goto no_config; + } + buf = confkey-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--) { -- 2.14.2.920.gcf0c67979c-goog