Patch "sysfs: fix race between readdir and lseek" has been added to the 3.8-stable tree

[<gregkh@linuxfoundation.org>]

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

    sysfs: fix race between readdir and lseek

to the 3.8-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:
     sysfs-fix-race-between-readdir-and-lseek.patch
and it can be found in the queue-3.8 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 991f76f837bf22c5bb07261cfd86525a0a96650c Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@canonical.com>
Date: Wed, 20 Mar 2013 23:25:24 +0800
Subject: sysfs: fix race between readdir and lseek

From: Ming Lei <ming.lei@canonical.com>

commit 991f76f837bf22c5bb07261cfd86525a0a96650c upstream.

While readdir() is running, lseek() may set filp->f_pos as zero,
then may leave filp->private_data pointing to one sysfs_dirent
object without holding its reference counter, so the sysfs_dirent
object may be used after free in next readdir().

This patch holds inode->i_mutex to avoid the problem since
the lock is always held in readdir path.

Reported-by: Dave Jones <davej@redhat.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/sysfs/dir.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -1058,10 +1058,21 @@ static int sysfs_readdir(struct file * f
 	return 0;
 }
 
+static loff_t sysfs_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *inode = file->f_path.dentry->d_inode;
+	loff_t ret;
+
+	mutex_lock(&inode->i_mutex);
+	ret = generic_file_llseek(file, offset, whence);
+	mutex_unlock(&inode->i_mutex);
+
+	return ret;
+}
 
 const struct file_operations sysfs_dir_operations = {
 	.read		= generic_read_dir,
 	.readdir	= sysfs_readdir,
 	.release	= sysfs_dir_release,
-	.llseek		= generic_file_llseek,
+	.llseek		= sysfs_dir_llseek,
 };


Patches currently in stable-queue which might be from ming.lei@canonical.com are

queue-3.8/bluetooth-add-support-for-dell.patch
queue-3.8/sysfs-handle-failure-path-correctly-for-readdir.patch
queue-3.8/bluetooth-add-support-for-dell_2.patch
queue-3.8/sysfs-fix-race-between-readdir-and-lseek.patch