Patch "fscrypto: require write access to mount to set encryption policy" has been added to the 4.4-stable tree

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

fscrypto: require write access to mount to set encryption policy

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:
fscrypto-require-write-access-to-mount-to-set-encryption-policy.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 <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Thu, 8 Sep 2016 14:20:38 -0700
Subject: fscrypto: require write access to mount to set encryption policy

commit ba63f23d69a3a10e7e527a02702023da68ef8a6d upstream.

[Please apply to 4.4-stable. Note: this was already backported, but only to ext4; it was missed that it should go to f2fs as well. This is needed to make xfstest generic/395 pass on f2fs.]

Since setting an encryption policy requires writing metadata to the filesystem, it should be guarded by mnt_want_write/mnt_drop_write. Otherwise, a user could cause a write to a frozen or readonly filesystem. This was handled correctly by f2fs but not by ext4. Make fscrypt_process_policy() handle it rather than relying on the filesystem to get it right.

---
 fs/f2fs/file.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -1541,12 +1541,18 @@ static int f2fs_ioc_set_encryption_polic
 				sizeof(policy)))
 		return -EFAULT;
 
+	err = mnt_want_write_file(filp);
+	if (err)
+		return err;
+
 	mutex_lock(&inode->i_mutex);
 
 	err = f2fs_process_policy(&policy, inode);
 
 	mutex_unlock(&inode->i_mutex);
 
+	mnt_drop_write_file(filp);
+
 	return err;
 #else
 	return -EOPNOTSUPP;

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