linux-kernel - Re: [PATCH v2 03/10] blktrace: fix debugfs use after free

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Message-ID: <20200420184607.GL11244@42.do-not-panic.com>
Date:   Mon, 20 Apr 2020 18:46:07 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     axboe@...nel.dk, viro@...iv.linux.org.uk,
        gregkh@...uxfoundation.org, rostedt@...dmis.org, mingo@...hat.com,
        jack@...e.cz, ming.lei@...hat.com, nstange@...e.de,
        akpm@...ux-foundation.org, mhocko@...e.com, yukuai3@...wei.com,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Omar Sandoval <osandov@...com>,
        Hannes Reinecke <hare@...e.com>,
        Michal Hocko <mhocko@...nel.org>,
        syzbot+603294af2d01acfdd6da@...kaller.appspotmail.com
Subject: Re: [PATCH v2 03/10] blktrace: fix debugfs use after free

On Sun, Apr 19, 2020 at 05:38:59PM -0700, Bart Van Assche wrote:
> On 4/19/20 5:04 PM, Luis Chamberlain wrote:
> > > Independent of what the purpose of the above code is, can that code be
> > > rewritten such that it does not depend on the details of how names are
> > > assigned to disks and partitions? Would disk_get_part() be useful here?
> > 
> > I did try, but couldn't figure out a way. I'll keep looking but likewise
> > let me know if you find a way.
> 
> How about making blk_trace_setup() pass the result of the following
> expression as an additional argument to blk_trace_setup():
> 
> 	bdev != bdev->bd_contains
> 
> I think that is a widely used approach to verify after a block device has
> been opened whether or not 'bdev' refers to a partition (bdev !=
> bdev->bd_contains means that 'bdev' represents a partition).

Sweet, that should simplify this considerbly, thanks!

  Luis