Commit 192cabd6 authored by Eric Biggers's avatar Eric Biggers Committed by David Howells

lib/digsig: fix dereference of NULL user_key_payload

digsig_verify() requests a user key, then accesses 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 acquire its semaphore.

Fix it by checking for a NULL payload, treating it like a key which was
already revoked at the time it was requested.

Fixes: 051dbb91 ("crypto: digital signature verification support")
Reviewed-by: 's avatarJames Morris <james.l.morris@oracle.com>
Cc: <stable@vger.kernel.org>    [v3.3+]
Cc: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: 's avatarEric Biggers <ebiggers@google.com>
Signed-off-by: 's avatarDavid Howells <dhowells@redhat.com>
parent d124b2c5
......@@ -87,6 +87,12 @@ static int digsig_verify_rsa(struct key *key,
down_read(&key->sem);
ukp = user_key_payload_locked(key);
if (!ukp) {
/* key was revoked before we acquired its semaphore */
err = -EKEYREVOKED;
goto err1;
}
if (ukp->datalen < sizeof(*pkh))
goto err1;
......
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