From: Ming Lei <ming.lei@canonical.com>
Date: Wed, 20 Mar 2013 15:25:24 +0000 (+0800)
Subject: sysfs: fix race between readdir and lseek
X-Git-Tag: v3.2.43~54
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=76bfc5ab57137d351a9046a002ee39a220d0e012;p=pandora-kernel.git

sysfs: fix race between readdir and lseek

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>
[bwh: Backported to 3.2: open-code file_inode() which we don't have]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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