Patch "debugfs: fix refcount imbalance in start_creating" has been added to the 4.1-stable tree

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

debugfs: fix refcount imbalance in start_creating

to the 4.1-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:
debugfs-fix-refcount-imbalance-in-start_creating.patch
and it can be found in the queue-4.1 subdirectory.

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

From: Daniel Borkmann <[email protected]>
Date: Thu, 5 Nov 2015 00:01:51 +0100
Subject: debugfs: fix refcount imbalance in start_creating

From: Daniel Borkmann <[email protected]>

commit 0ee9608c89e81a1ccee52ecb58a7ff040e2522d9 upstream.

In debugfs' start_creating(), we pin the file system to safely access its root. When we failed to create a file, we unpin the file system via failed_creating() to release the mount count and eventually the reference of the vfsmount.

However, when we run into an error during lookup_one_len() when still in start_creating(), we only release the parent's mutex but not so the reference on the mount. Looks like it was done in the past, but after splitting portions of __create_file() into start_creating() and end_creating() via 190afd81e4a5 ("debugfs: split the beginning and the end of __create_file() off"), this seemed missed. Noticed during code review.

---
 fs/debugfs/inode.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -276,8 +276,12 @@ static struct dentry *start_creating(con
 		dput(dentry);
 		dentry = ERR_PTR(-EEXIST);
 	}
-	if (IS_ERR(dentry))
+
+	if (IS_ERR(dentry)) {
 		mutex_unlock(&d_inode(parent)->i_mutex);
+		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+	}
+
 	return dentry;
 }
 

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

queue-4.1/packet-infer-protocol-from-ethernet-header-if-unset.patch queue-4.1/debugfs-fix-refcount-imbalance-in-start_creating.patch queue-4.1/bpf-array-fix-heap-out-of-bounds-access-when-updating-elements.patch queue-4.1/ipv6-sctp-implement-sctp_v6_destroy_sock.patch queue-4.1/packet-only-allow-extra-vlan-len-on-ethernet-devices.patch queue-4.1/net-scm-fix-pax-detected-msg_controllen-overflow-in-scm_detach_fds.patch queue-4.1/packet-fix-tpacket_snd-max-frame-len.patch queue-4.1/packet-always-probe-for-transport-header.patch queue-4.1/packet-do-skb_probe_transport_header-when-we-actually-have-data.patch queue-4.1/tools-net-use-include-uapi-with-__exported_headers__.patch