Patch "FS-Cache: fix dereference of NULL user_key_payload" has been added to the 4.13-stable tree

[<gregkh@linuxfoundation.org>]

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 4.13-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-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From d124b2c53c7bee6569d2a2d0b18b4a1afde00134 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Mon, 9 Oct 2017 12:40:00 -0700
Subject: FS-Cache: fix dereference of NULL user_key_payload

From: Eric Biggers <ebiggers@google.com>

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 <james.l.morris@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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+		/* key was revoked */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--) {


Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.13/keys-fix-race-between-updating-and-finding-a-negative-key.patch
queue-4.13/fs-cache-fix-dereference-of-null-user_key_payload.patch
queue-4.13/lib-digsig-fix-dereference-of-null-user_key_payload.patch
queue-4.13/ecryptfs-fix-dereference-of-null-user_key_payload.patch
queue-4.13/fscrypt-fix-dereference-of-null-user_key_payload.patch
queue-4.13/keys-encrypted-fix-dereference-of-null-user_key_payload.patch
queue-4.13/keys-don-t-let-add_key-update-an-uninstantiated-key.patch