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md: fix use-after-free bug when dropping an rdev from an md array 

Due to possible deadlock issues we need to use a schedule work to kobject_del
an 'rdev' object from a different thread.

A recent change means that kobject_add no longer gets a refernce, and
kobject_del doesn't put a reference.  Consequently, we need to explicitly hold
a reference to ensure that the last reference isn't dropped before the
scheduled work get a chance to call kobject_del.

Also, rename delayed_delete to md_delayed_delete to that it is more obvious in
a stack trace which code is to blame.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
NeilBrown 2008-02-06 01:39:56 -08:00 committed by Linus Torvalds
parent a17184a911
commit 177a99b23e
1 changed files with 5 additions and 3 deletions
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8
drivers/md/md.c
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@ -1419,10 +1419,11 @@ static int bind_rdev_to_array(mdk_rdev_t * rdev, mddev_t * mddev)
return err;
}
static void delayed_delete(struct work_struct *ws)
static void md_delayed_delete(struct work_struct *ws)
{
mdk_rdev_t *rdev = container_of(ws, mdk_rdev_t, del_work);
kobject_del(&rdev->kobj);
kobject_put(&rdev->kobj);
}
static void unbind_rdev_from_array(mdk_rdev_t * rdev)
@ -1441,7 +1442,8 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev)
/* We need to delay this, otherwise we can deadlock when
* writing to 'remove' to "dev/state"
*/
INIT_WORK(&rdev->del_work, delayed_delete);
INIT_WORK(&rdev->del_work, md_delayed_delete);
kobject_get(&rdev->kobj);
schedule_work(&rdev->del_work);
}
@ -3686,7 +3688,7 @@ static int do_md_stop(mddev_t * mddev, int mode)
sysfs_remove_link(&mddev->kobj, nm);
}
/* make sure all delayed_delete calls have finished */
/* make sure all md_delayed_delete calls have finished */
flush_scheduled_work();
export_array(mddev);