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From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "josef@toxicpanda.com" <josef@toxicpanda.com>
Cc: "kernel-team@fb.com" <kernel-team@fb.com>,
	"jbacik@fb.com" <jbacik@fb.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"alex@iss-integration.com" <alex@iss-integration.com>,
	"nbd@other.debian.org" <nbd@other.debian.org>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH 1/3] nbd: del_gendisk after we cleanup the queue
Date: Fri, 13 Apr 2018 16:25:33 +0000	[thread overview]
Message-ID: <1f0ebe74a96c6515716a25b49ea588f9ee28e137.camel@wdc.com> (raw)
In-Reply-To: <20180413162132.xudowhvxyijbzqqa@destiny>

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WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "josef@toxicpanda.com" <josef@toxicpanda.com>
Cc: "kernel-team@fb.com" <kernel-team@fb.com>,
	"jbacik@fb.com" <jbacik@fb.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"alex@iss-integration.com" <alex@iss-integration.com>,
	"nbd@other.debian.org" <nbd@other.debian.org>,
	"axboe@kernel.dk" <axboe@kernel.dk>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH 1/3] nbd: del_gendisk after we cleanup the queue
Date: Fri, 13 Apr 2018 16:25:33 +0000	[thread overview]
Message-ID: <1f0ebe74a96c6515716a25b49ea588f9ee28e137.camel@wdc.com> (raw)
In-Reply-To: <20180413162132.xudowhvxyijbzqqa@destiny>

On Fri, 2018-04-13 at 12:21 -0400, Josef Bacik wrote:
> On Fri, Apr 13, 2018 at 04:16:18PM +0000, Bart Van Assche wrote:
> > On Fri, 2018-04-13 at 12:03 -0400, Josef Bacik wrote:
> > > This fixes a use after free bug, we need to do the del_gendisk after we
> > > cleanup the queue on the device.
> > 
> > Hello Josef,
> > 
> > Which use-after-free bug does this patch fix? Are you aware that most block
> > drivers call blk_cleanup_queue() before calling del_gendisk()? Why do you
> > think that the nbd driver should use the opposite order?
> 
> I'm confused, that's what this patch does.  Before I had del_gendisk() first and
> then the blk_cleanup_queue(), which was bugging out when I was testing stuff
> with a null pointer deref whenever I rmmod'ed the nbd.  Swapping it to the way
> everybody else did it fixed the problem.  Thanks,

Hello Josef,

Oops, I swapped "blk_cleanup_queue()" and "del_gendisk()" in my e-mail.

Can you share the call stack of the NULL pointer deref and also the translation
of the crash address into a source code line?

Thanks,

Bart.



  reply	other threads:[~2018-04-13 16:25 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-13 16:03 [PATCH 1/3] nbd: del_gendisk after we cleanup the queue Josef Bacik
2018-04-13 16:03 ` [PATCH 2/3] nbd: update size when connected Josef Bacik
2018-04-14  3:02   ` Alex Gorbachev
2018-04-13 16:03 ` [PATCH 3/3] nbd: use bd_set_size when updating disk size Josef Bacik
2018-04-14  3:01   ` Alex Gorbachev
2018-04-13 16:16 ` [PATCH 1/3] nbd: del_gendisk after we cleanup the queue Bart Van Assche
2018-04-13 16:16   ` Bart Van Assche
2018-04-13 16:21   ` Josef Bacik
2018-04-13 16:25     ` Bart Van Assche [this message]
2018-04-13 16:25       ` Bart Van Assche
2018-04-14  3:03 ` Alex Gorbachev

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