APPLIED: [CVE-2014-9529][Lucid] KEYS: close race between key lookup and freeing
Brad Figg
brad.figg at canonical.com
Thu Jan 15 19:05:16 UTC 2015
On Wed, Jan 14, 2015 at 04:47:30PM +0000, Luis Henriques wrote:
> From: Sasha Levin <sasha.levin at oracle.com>
>
> When a key is being garbage collected, it's key->user would get put before
> the ->destroy() callback is called, where the key is removed from it's
> respective tracking structures.
>
> This leaves a key hanging in a semi-invalid state which leaves a window open
> for a different task to try an access key->user. An example is
> find_keyring_by_name() which would dereference key->user for a key that is
> in the process of being garbage collected (where key->user was freed but
> ->destroy() wasn't called yet - so it's still present in the linked list).
>
> This would cause either a panic, or corrupt memory.
>
> Fixes CVE-2014-9529.
>
> Signed-off-by: Sasha Levin <sasha.levin at oracle.com>
> Signed-off-by: David Howells <dhowells at redhat.com>
> (backported from commit a3a8784454692dd72e5d5d34dcdab17b4420e74c)
> CVE-2014-9529
> BugLink: http://bugs.launchpad.net/bugs/1409048
> Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
> ---
> security/keys/key.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/security/keys/key.c b/security/keys/key.c
> index e50d264c9ad1..27d5ad7c4a4d 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -577,12 +577,12 @@ static void key_cleanup(struct work_struct *work)
> if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
> atomic_dec(&key->user->nikeys);
>
> - key_user_put(key->user);
> -
> /* now throw away the key memory */
> if (key->type->destroy)
> key->type->destroy(key);
>
> + key_user_put(key->user);
> +
> kfree(key->description);
>
> #ifdef KEY_DEBUGGING
> --
> 2.1.4
>
> --
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Applied to Lucid master-next
--
Brad Figg brad.figg at canonical.com http://www.canonical.com
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