From 192cabd6a296cbc57b3d8c05c4c89d87fc102506 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 9 Oct 2017 12:43:20 -0700 Subject: 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: 051dbb918c7f ("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 --- lib/digsig.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'lib') diff --git a/lib/digsig.c b/lib/digsig.c index 03d7c63..6ba6fcd 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sem); ukp = user_key_payload_locked(key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + err = -EKEYREVOKED; + goto err1; + } + if (ukp-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; -- cgit v1.1