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>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index b757da1..e71c5fa 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6044,9 +6044,8 @@
|| kthread_should_stop(),
thread->timeout);
- clear_bit(THREAD_WAKEUP, &thread->flags);
-
- thread->run(thread->mddev);
+ if (test_and_clear_bit(THREAD_WAKEUP, &thread->flags))
+ thread->run(thread->mddev);
}
return 0;