[3.19.y-ckt stable] Patch "ufs: Fix possible deadlock when looking up directories" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ufs: Fix possible deadlock when looking up directories

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.y-ckt4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6b1f77a9b2b5dd9b249c96a37d64f341edd6b757 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack at suse.cz>
Date: Tue, 2 Jun 2015 11:26:34 +0200
Subject: ufs: Fix possible deadlock when looking up directories

commit 514d748f69c97a51a2645eb198ac5c6218f22ff9 upstream.

Commit e4502c63f56aeca88 (ufs: deal with nfsd/iget races) made ufs
create inodes with I_NEW flag set. However ufs_mkdir() never cleared
this flag. Thus if someone ever tried to lookup the directory by inode
number, he would deadlock waiting for I_NEW to be cleared. Luckily this
mostly happens only if the filesystem is exported over NFS since
otherwise we have the inode attached to dentry and don't look it up by
inode number. In rare cases dentry can get freed without inode being
freed and then we'd hit the deadlock even without NFS export.

Fix the problem by clearing I_NEW before instantiating new directory
inode.

Fixes: e4502c63f56aeca887ced37f24e0def1ef11cec8
Reported-by: Fabian Frederick <fabf at skynet.be>
Signed-off-by: Jan Kara <jack at suse.cz>
Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ufs/namei.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ufs/namei.c b/fs/ufs/namei.c
index 6515899..73644c6 100644
--- a/fs/ufs/namei.c
+++ b/fs/ufs/namei.c
@@ -207,6 +207,7 @@ static int ufs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
 		goto out_fail;
 	unlock_ufs(dir->i_sb);

+	unlock_new_inode(inode);
 	d_instantiate(dentry, inode);
 out:
 	return err;
--
1.9.1