Commit 589a594b authored Dec 09, 2010 by NeilBrown

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>

parent 1a855a06

drivers/md/md.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -6044,8 +6044,7 @@ static int md_thread(void * arg)
		\|\| kthread_should_stop(),
		thread->timeout);

		clear_bit(THREAD_WAKEUP, &thread->flags);

		if (test_and_clear_bit(THREAD_WAKEUP, &thread->flags))
		thread->run(thread->mddev);
		}

drivers/md/raid10.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2397,13 +2397,13 @@ static int run(mddev_t *mddev)
		return 0;

		out_free_conf:
		md_unregister_thread(mddev->thread);
		if (conf->r10bio_pool)
		mempool_destroy(conf->r10bio_pool);
		safe_put_page(conf->tmppage);
		kfree(conf->mirrors);
		kfree(conf);
		mddev->private = NULL;
		md_unregister_thread(mddev->thread);
		out:
		return -EIO;
		}

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