Patch "sysfs: fix race between readdir and lseek" has been added to the 3.4-stable tree

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 3.4-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:
sysfs-fix-race-between-readdir-and-lseek.patch
and it can be found in the queue-3.4 subdirectory.

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

From: Ming Lei <[email protected]>
Date: Wed, 20 Mar 2013 23:25:24 +0800
Subject: sysfs: fix race between readdir and lseek

From: Ming Lei <[email protected]>

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.

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

@@ -1040,10 +1040,21 @@ 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_inode(file);
+	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 [email protected] are

queue-3.4/bluetooth-add-support-for-dell.patch queue-3.4/sysfs-handle-failure-path-correctly-for-readdir.patch queue-3.4/bluetooth-add-support-for-dell_2.patch queue-3.4/sysfs-fix-race-between-readdir-and-lseek.patch