linux-kernel - Re: [patch 02/52] fs: fix superblock iteration race

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Message-ID: <AANLkTinr_Ljn48o3YecbuYt15xbP02sbg9D6qqobt1wE@mail.gmail.com>
Date:	Tue, 29 Jun 2010 10:52:03 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	John Stultz <johnstul@...ibm.com>,
	Frank Mayhar <fmayhar@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [patch 02/52] fs: fix superblock iteration race

On Tue, Jun 29, 2010 at 10:41 AM, Nick Piggin <npiggin@...e.de> wrote:
> On Tue, Jun 29, 2010 at 10:35:47AM -0700, Linus Torvalds wrote:
>>
>> I'll apply it. We have a couple of oopses listed for the superblock
>> iterator, and I haven't heard from Al. And the patch looks obviously
>> fine, whether it's actually the cause of some of the bugs or not.
>
> OK. I only have managed to get it into an infininte loop but I think
> it would be surely possible to oops it because the next pointer can
> be uninitialised memory at that point.

Look for "2.6.35-rc3 oops trying to suspend" on lkml, for example. No
guarantee that it's the same thing, but it's "iterate_supers()"
getting an oops when it does "down_read(&sb->s_umount)". Which really
looks suspiciously like "sb" just being totally bogus, most likely
because of this same issue.

So I dunno, but I asked Al to look at it, and haven't heard back.

Regardless, I think your patch is the right thing to do (modulo any
syntactic issues - and I think your final version was the best of the
lot).

                    Linus
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