Patch "FS-Cache: fix dereference of NULL user_key_payload" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

FS-Cache: fix dereference of NULL user_key_payload

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fs-cache-fix-dereference-of-null-user_key_payload.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Mon, 9 Oct 2017 12:40:00 -0700
Subject: FS-Cache: fix dereference of NULL user_key_payload

From: Eric Biggers <[email protected]>

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.

---
 fs/fscache/object-list.c |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -330,6 +330,13 @@ static void fscache_objlist_config(struc
 	rcu_read_lock();
 
 	confkey = key->payload.data;
+	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+		/* key was revoked */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--) {

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/fs-cache-fix-dereference-of-null-user_key_payload.patch queue-3.18/lib-digsig-fix-dereference-of-null-user_key_payload.patch queue-3.18/keys-encrypted-fix-dereference-of-null-user_key_payload.patch queue-3.18/keys-don-t-let-add_key-update-an-uninstantiated-key.patch