Re: block: Fix oops caused by __blkdev_get() calling disk_unblock_events()with invalid @disk

[Jens Axboe]

On 2011-03-09 16:38, Tejun Heo wrote:
> Commit 57c966b8b2 (block: Don't check events while open is in
> progress) made __blkdev_get() block events around open calls; however,
> it used invalid @disk pointer in the following cases.
> 
> * When ->open() returns -ERESTARTSYS, disk_unblock_events() is called
>   after @disk is put.  @disk may be invalid by the time unblock is
>   called.
> 
>   This is fixed by moving references after disk_unblock_events().
> 
> * When there are multiple openers, @disk is cleared to %NULL and later
>   disk_unblock_disk() is called with %NULL @disk causing oops.
> 
>   This is fixed by moving reference putting after open success is
>   determined and not clearing @disk to %NULL.  On success, @disk is
>   valid because there is another opener holding reference to it.  On
>   failure, the references are put after disk_unblock_events() is
>   called.

Thanks, applied. A bit unfortunate to have a 100% crasher in the tree,
though. Will suck for bisects.

-- 
Jens Axboe

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