patch "sysfs: fix race between readdir and lseek" added to driver-core 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 my driver-core git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
in the driver-core-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

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

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(-)

index 2fbdff6..c9e1660 100644
@@ -1058,10 +1058,21 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 	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,
 };

1.8.0.rc0.18.gf84667d