[PATCH 2/7] FS-Cache: fix dereference of NULL user_key_payload

[James Morris]

On Thu, 28 Sep 2017, Eric Biggers wrote:

> From: Eric Biggers <ebiggers at google.com>
> 
> 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")
> Cc: <stable at vger.kernel.org>    [v2.6.32+]
> Signed-off-by: Eric Biggers <ebiggers at google.com>


Reviewed-by: James Morris <james.l.morris at oracle.com>


-- 
James Morris
<jmorris at namei.org>

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