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Commit 589a594b authored by NeilBrown's avatar NeilBrown
Browse files

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: default avatar"Citizen" <citizen_lee@thecus.com>
Signed-off-by: default avatarNeilBrown <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;

}