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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@ -6044,9 +6044,8 @@ static int md_thread(void * arg)
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|| kthread_should_stop(),
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thread->timeout);
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clear_bit(THREAD_WAKEUP, &thread->flags);
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thread->run(thread->mddev);
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if (test_and_clear_bit(THREAD_WAKEUP, &thread->flags))
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thread->run(thread->mddev);
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}
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return 0;
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@ -2397,13 +2397,13 @@ static int run(mddev_t *mddev)
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return 0;
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out_free_conf:
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md_unregister_thread(mddev->thread);
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if (conf->r10bio_pool)
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mempool_destroy(conf->r10bio_pool);
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safe_put_page(conf->tmppage);
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kfree(conf->mirrors);
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kfree(conf);
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mddev->private = NULL;
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md_unregister_thread(mddev->thread);
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out:
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return -EIO;
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}
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