From: NeilBrown <neilb@suse.de>
Date: Thu, 9 Dec 2010 06:02:14 +0000 (+1100)
Subject: md: protect against NULL reference when waiting to start a raid10.
X-Git-Tag: v2.6.37-rc6~7^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=589a594be1fb8815b3f18e517be696c48664f728;p=pandora-kernel.git

md: protect against NULL reference when waiting to start a raid10.

When we fail to start a raid10 for some reason, we call
md_unregister_thread to kill the thread that was created.

Unfortunately md_thread() will then make one call into the handler
(raid10d) even though md_wakeup_thread has not been called.  This is
not safe and as md_unregister_thread is called after mddev->private
has been set to NULL, it will definitely cause a NULL dereference.

So fix this at both ends:
 - md_thread should only call the handler if THREAD_WAKEUP has been
   set.
 - raid10 should call md_unregister_thread before setting things
   to NULL just like all the other raid modules do.

This is applicable to 2.6.35 and later.

Cc: stable@kernel.org
Reported-by: "Citizen" <citizen_lee@thecus.com>
Signed-off-by: NeilBrown <neilb@suse.de>
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