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 4.9-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-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d124b2c53c7bee6569d2a2d0b18b4a1afde00134 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Date: Mon, 9 Oct 2017 12:40:00 -0700
Subject: FS-Cache: fix dereference of NULL user_key_payload
From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(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+ /* key was revoked */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@xxxxxxxxxx are
queue-4.9/keys-fix-race-between-updating-and-finding-a-negative-key.patch
queue-4.9/fs-cache-fix-dereference-of-null-user_key_payload.patch
queue-4.9/lib-digsig-fix-dereference-of-null-user_key_payload.patch
queue-4.9/fscrypt-fix-dereference-of-null-user_key_payload.patch
queue-4.9/keys-encrypted-fix-dereference-of-null-user_key_payload.patch
queue-4.9/keys-don-t-let-add_key-update-an-uninstantiated-key.patch