From: Eric Biggers <ebiggers@xxxxxxxxxx>
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: 051dbb918c7f ("crypto: digital signature verification support")
Reviewed-by: James Morris <james.l.morris@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [v3.3+]
Cc: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
Changed since v1: added Reviewed-by and resent as standalone patch. Can
this please be taken through the security tree or the keyrings tree?
lib/digsig.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/lib/digsig.c b/lib/digsig.c
index 03d7c63837ae..6ba6fcd92dd1 100644
--- a/lib/digsig.c
+++ b/lib/digsig.c
@@ -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+ /* key was revoked before we acquired its semaphore */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;
--
2.14.2.920.gcf0c67979c-goog