linux-kernel - Re: [PATCH 7/7] blktrace: avoid accessing NULL bdev->bd

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Message-ID: <20090320130839.GM30407@ghostprotocols.net>
Date:	Fri, 20 Mar 2009 10:08:39 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Jens Axboe <jens.axboe@...cle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/7] blktrace: avoid accessing NULL bdev->bd_disk

Em Fri, Mar 20, 2009 at 09:49:48AM +0800, Li Zefan escreveu:
> bdev->bd_disk can be NULL, if the block device is not opened.
> 
> Try this against an unmounted partition, and you'll see NULL dereference:
>   # echo 1 > /sys/block/sda/sda5/enable
> 
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>

I guess this can be discounted on my block layer newbeeness 8)

But as an extra check in non hot-paths are usually a good thing...

Acked-by: Arnaldo Carvalho de Melo <acme@...hat.com>

- Arnaldo
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