From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiggers3@gmail.com (Eric Biggers) Date: Mon, 9 Oct 2017 12:43:20 -0700 Subject: [PATCH v2] lib/digsig: fix dereference of NULL user_key_payload Message-ID: <20171009194320.67221-1-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") Reviewed-by: James Morris Cc: [v3.3+] Cc: Dmitry Kasatkin Signed-off-by: Eric Biggers --- 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sem); ukp = user_key_payload_locked(key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + err = -EKEYREVOKED; + goto err1; + } + if (ukp-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 -- 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