ecryptfs: fix dereference of NULL user_key_payload
authorEric Biggers <ebiggers@google.com>
Mon, 9 Oct 2017 19:51:27 +0000 (12:51 -0700)
committerDavid Howells <dhowells@redhat.com>
Thu, 12 Oct 2017 16:16:40 +0000 (17:16 +0100)
commitf66665c09ab489a11ca490d6a82df57cfc1bea3e
tree8bcdb1a0fa653b839656e246aeefa7484e17a025
parentd60b5b7854c3d135b869f74fb93eaf63cbb1991a
ecryptfs: fix dereference of NULL user_key_payload

In eCryptfs, we failed to verify that the authentication token keys are
not revoked before dereferencing their payloads, which is problematic
because the payload of a revoked key is NULL.  request_key() *does* skip
revoked keys, but there is still a window where the key can be revoked
before we acquire the key semaphore.

Fix it by updating ecryptfs_get_key_payload_data() to return
-EKEYREVOKED if the key payload is NULL.  For completeness we check this
for "encrypted" keys as well as "user" keys, although encrypted keys
cannot be revoked currently.

Alternatively we could use key_validate(), but since we'll also need to
fix ecryptfs_get_key_payload_data() to validate the payload length, it
seems appropriate to just check the payload pointer.

Fixes: 237fead61998 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")
Reviewed-by: James Morris <james.l.morris@oracle.com>
Cc: <stable@vger.kernel.org> [v2.6.19+]
Cc: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
fs/ecryptfs/ecryptfs_kernel.h
fs/ecryptfs/keystore.c