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: 051dbb918c ("crypto: digital signature verification support")
Reviewed-by: James Morris <>
Cc: <>    [v3.3+]
Cc: Dmitry Kasatkin <>
Signed-off-by: Eric Biggers <>
Signed-off-by: David Howells <>
Eric Biggers 6 years ago committed by David Howells
parent d124b2c53c
commit 192cabd6a2

@ -87,6 +87,12 @@ static int digsig_verify_rsa(struct key *key,
ukp = user_key_payload_locked(key);
if (!ukp) {
/* key was revoked before we acquired its semaphore */
goto err1;
if (ukp->datalen < sizeof(*pkh))
goto err1;