Patch "fscrypt: fix dereference of NULL user_key_payload" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

fscrypt: fix dereference of NULL user_key_payload

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fscrypt-fix-dereference-of-null-user_key_payload.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Mon, 9 Oct 2017 12:46:18 -0700
Subject: fscrypt: fix dereference of NULL user_key_payload

From: Eric Biggers <[email protected]>

commit d60b5b7854c3d135b869f74fb93eaf63cbb1991a upstream.

When an fscrypt-encrypted file is opened, we request the file's master key from the keyrings service as a logon key, then access 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.

---
 fs/crypto/keyinfo.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -108,6 +108,11 @@ static int validate_user_key(struct fscr
 		goto out;
 	}
 	ukp = user_key_payload(keyring_key);
+	if (!ukp) {
+		/* key was revoked before we acquired its semaphore */
+		res = -EKEYREVOKED;
+		goto out;
+	}
 	if (ukp->datalen != sizeof(struct fscrypt_key)) {
 		res = -EINVAL;
 		goto out;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/keys-fix-race-between-updating-and-finding-a-negative-key.patch queue-4.9/fs-cache-fix-dereference-of-null-user_key_payload.patch queue-4.9/lib-digsig-fix-dereference-of-null-user_key_payload.patch queue-4.9/fscrypt-fix-dereference-of-null-user_key_payload.patch queue-4.9/keys-encrypted-fix-dereference-of-null-user_key_payload.patch queue-4.9/keys-don-t-let-add_key-update-an-uninstantiated-key.patch