[ 3.5.y.z extended stable ] Patch "sysfs: handle failure path correctly for readdir()" has been added to staging queue

[Luis Henriques]

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

    sysfs: handle failure path correctly for readdir()

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

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

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From b670cfa86079178781f7ad2669e5bc78761d7d7b Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei at canonical.com>
Date: Wed, 20 Mar 2013 23:25:25 +0800
Subject: [PATCH] sysfs: handle failure path correctly for readdir()

commit e5110f411d2ee35bf8d202ccca2e89c633060dca upstream.

In case of 'if (filp->f_pos ==  0 or 1)' of sysfs_readdir(),
the failure from filldir() isn't handled, and the reference counter
of the sysfs_dirent object pointed by filp->private_data will be
released without clearing filp->private_data, so use after free
bug will be triggered later.

This patch returns immeadiately under the situation for fixing the bug,
and it is reasonable to return from readdir() when filldir() fails.

Reported-by: Dave Jones <davej at redhat.com>
Tested-by: Sasha Levin <levinsasha928 at gmail.com>
Signed-off-by: Ming Lei <ming.lei at canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/sysfs/dir.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 5a035b5..2ee0864 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -1021,6 +1021,8 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 		ino = parent_sd->s_ino;
 		if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)
 			filp->f_pos++;
+		else
+			return 0;
 	}
 	if (filp->f_pos == 1) {
 		if (parent_sd->s_parent)
@@ -1029,6 +1031,8 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 			ino = parent_sd->s_ino;
 		if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)
 			filp->f_pos++;
+		else
+			return 0;
 	}
 	mutex_lock(&sysfs_mutex);
 	for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);
--
1.8.1.2