From 4c3bffc272755c98728c2b58b1a8148cf9e9fd1f Mon Sep 17 00:00:00 2001
From: Chen Gang <gang.chen@asianux.com>
Date: Wed, 11 Sep 2013 14:22:44 -0700
Subject: [PATCH] mm/backing-dev.c: check user buffer length before copying
 data to the related user buffer

'*lenp' may be less than "sizeof(kbuf)" so we must check this before the
next copy_to_user().

pdflush_proc_obsolete() is called by sysctl which 'procname' is
"nr_pdflush_threads", if the user passes buffer length less than
"sizeof(kbuf)", it will cause issue.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
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