linux-kernel - Re: [PATCH v2] block: Fix use-after-free in blkdev

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Message-ID: <20200605144236.GB13248@quack2.suse.cz>
Date:   Fri, 5 Jun 2020 16:42:36 +0200
From:   Jan Kara <jack@...e.cz>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Jason Yan <yanaijie@...wei.com>, Jan Kara <jack@...e.cz>,
        Markus Elfring <Markus.Elfring@....de>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        hulkci@...wei.com, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Ming Lei <ming.lei@...hat.com>
Subject: Re: [PATCH v2] block: Fix use-after-free in blkdev_get()

On Fri 05-06-20 12:43:54, Dan Carpenter wrote:
> I wonder if maybe the best fix is to re-add the "if (!res) " check back
> to blkdev_get().

Well, it won't be that simple since we need to call bd_abort_claiming()
under bdev->bd_mutex. And the fact that __blkdev_get() frees the reference
you pass to it is somewhat subtle and surprising so I think we are better
off getting rid of that.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR