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[3/7] lib/digsig: fix dereference of NULL user_key_payload

Message ID 20170928212602.41744-4-ebiggers3@gmail.com (mailing list archive)
State Not Applicable
Headers show

Commit Message

Eric Biggers Sept. 28, 2017, 9:25 p.m. UTC 
From: Eric Biggers <ebiggers@google.com>

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: <stable@vger.kernel.org>    [v3.3+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 lib/digsig.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

James Morris Oct. 3, 2017, 10:52 a.m. UTC | #1 
On Thu, 28 Sep 2017, Eric Biggers wrote:

> From: Eric Biggers <ebiggers@google.com>
> 
> 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: <stable@vger.kernel.org>    [v3.3+]
> Signed-off-by: Eric Biggers <ebiggers@google.com>


Reviewed-by: James Morris <james.l.morris@oracle.com>
diff mbox

Patch

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+		/* key was revoked before we acquired its semaphore */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;