linux-ext4 - [PATCH] fs: Avoid userspace mounting anon

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Date:	Fri, 10 Oct 2014 16:23:22 +0200
From:	Jan Kara <jack@...e.cz>
To:	linux-fsdevel@...r.kernel.org
Cc:	linux-ext4@...r.kernel.org, Dave Chinner <david@...morbit.com>,
	xfs@....sgi.com, cluster-devel@...hat.com,
	Steven Whitehouse <swhiteho@...hat.com>,
	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <jlbec@...lplan.org>, ocfs2-devel@....oracle.com,
	reiserfs-devel@...r.kernel.org, Jeff Mahoney <jeffm@...e.de>,
	Dave Kleikamp <shaggy@...nel.org>,
	jfs-discussion@...ts.sourceforge.net, tytso@....edu,
	viro@...iv.linux.org.uk, Jan Kara <jack@...e.cz>
Subject: [PATCH] fs: Avoid userspace mounting anon_inodefs filesystem

anon_inodefs filesystem is a kernel internal filesystem userspace
shouldn't mess with. Remove registration of it so userspace cannot
even try to mount it (which would fail anyway because the filesystem is
MS_NOUSER).

This fixes an oops triggered by trinity when it tried mounting
anon_inodefs which overwrote anon_inode_inode pointer while other CPU
has been in anon_inode_getfile() between ihold() and d_instantiate().
Thus effectively creating dentry pointing to an inode without holding a
reference to it.

Reported-by: Sasha Levin <sasha.levin@...cle.com>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/anon_inodes.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 24084732b1d0..4b4543b8b894 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -177,9 +177,6 @@ static int __init anon_inode_init(void)
 {
 	int error;
 
-	error = register_filesystem(&anon_inode_fs_type);
-	if (error)
-		goto err_exit;
 	anon_inode_mnt = kern_mount(&anon_inode_fs_type);
 	if (IS_ERR(anon_inode_mnt)) {
 		error = PTR_ERR(anon_inode_mnt);
-- 
1.8.1.4

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