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

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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>
This commit is contained in:
NeilBrown 2010-12-09 17:02:14 +11:00
parent 1a855a0606
commit 589a594be1
2 changed files with 3 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

5
drivers/md/md.c
View file

@ -6044,9 +6044,8 @@ static int md_thread(void * arg)
|| 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;

2
drivers/md/raid10.c
View file

@ -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;
}