Patch "fscrypt: fix dereference of NULL user_key_payload" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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 4.4-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-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From d60b5b7854c3d135b869f74fb93eaf63cbb1991a Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Mon, 9 Oct 2017 12:46:18 -0700
Subject: fscrypt: fix dereference of NULL user_key_payload

From: Eric Biggers <ebiggers@google.com>

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.

Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
Reviewed-by: James Morris <james.l.morris@oracle.com>
Cc: <stable@vger.kernel.org>    [v4.1+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ext4/crypto_key.c |    6 ++++++
 fs/f2fs/crypto_key.c |    6 ++++++
 2 files changed, 12 insertions(+)

--- a/fs/ext4/crypto_key.c
+++ b/fs/ext4/crypto_key.c
@@ -204,6 +204,12 @@ int ext4_get_encryption_info(struct inod
 	}
 	down_read(&keyring_key->sem);
 	ukp = user_key_payload(keyring_key);
+	if (!ukp) {
+		/* key was revoked before we acquired its semaphore */
+		res = -EKEYREVOKED;
+		up_read(&keyring_key->sem);
+		goto out;
+	}
 	if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
 		res = -EINVAL;
 		up_read(&keyring_key->sem);
--- a/fs/f2fs/crypto_key.c
+++ b/fs/f2fs/crypto_key.c
@@ -195,6 +195,12 @@ int f2fs_get_encryption_info(struct inod
 	}
 	down_read(&keyring_key->sem);
 	ukp = user_key_payload(keyring_key);
+	if (!ukp) {
+		/* key was revoked before we acquired its semaphore */
+		res = -EKEYREVOKED;
+		up_read(&keyring_key->sem);
+		goto out;
+	}
 	if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
 		res = -EINVAL;
 		up_read(&keyring_key->sem);


Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.4/keys-fix-race-between-updating-and-finding-a-negative-key.patch
queue-4.4/fscrypto-require-write-access-to-mount-to-set-encryption-policy.patch
queue-4.4/fs-cache-fix-dereference-of-null-user_key_payload.patch
queue-4.4/lib-digsig-fix-dereference-of-null-user_key_payload.patch
queue-4.4/fscrypt-fix-dereference-of-null-user_key_payload.patch
queue-4.4/f2fs-crypto-add-missing-locking-for-keyring_key-access.patch
queue-4.4/keys-encrypted-fix-dereference-of-null-user_key_payload.patch
queue-4.4/f2fs-crypto-replace-some-bug_on-s-with-error-checks.patch
queue-4.4/keys-don-t-let-add_key-update-an-uninstantiated-key.patch