From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiggers3@gmail.com (Eric Biggers) Date: Thu, 28 Sep 2017 14:25:58 -0700 Subject: [PATCH 3/7] lib/digsig: fix dereference of NULL user_key_payload In-Reply-To: <20170928212602.41744-1-ebiggers3@gmail.com> References: <20170928212602.41744-1-ebiggers3@gmail.com> Message-ID: <20170928212602.41744-4-ebiggers3@gmail.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org From: Eric Biggers 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") Cc: [v3.3+] Signed-off-by: Eric Biggers --- 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sem); ukp = user_key_payload_locked(key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + err = -EKEYREVOKED; + goto err1; + } + if (ukp-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; -- 2.14.2.822.g60be5d43e6-goog -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info@ http://vger.kernel.org/majordomo-info.html