linux-kernel - Re: fs: NULL deref in atime_needs

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Date:	Fri, 26 Feb 2016 22:25:21 +0100
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Ian Kent <raven@...maw.net>,
	Mickaël Salaün <mic@...ikod.net>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: fs: NULL deref in atime_needs_update

On Fri, Feb 26, 2016 at 10:21 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Thu, Feb 25, 2016 at 04:39:27PM +0000, Al Viro wrote:
>> Hrm...  OK, seeing that you still seem to trigger those within an hour or
>> two (and *any* of remaining WARN_ON() are serious bugs - none of the
>> "mitigation had been triggered" remained, sorry for not making it clear),
>> let's try this.  Again, any WARN_ON triggered means that we'd caught something,
>> whether it progresses into oops or not.
>
> Any news on that one?  I'm going to carve fixes for understood bugs out of
> that one and put those into tonight push, but it would be nice to sort out
> all remaining crap lurking in that area...
>
> Another question: what about the very first trace you'd posted, with apparent
> GPF at 00000050?  Have you seen anything like that afterwards?

No, I did not have time to retest.

GPF at 00000050 was not mine, it was Mickaël's.

I did not try to reproduce mine first. But most likely it is the same
as the one I reproduced lately (GPF at NULL in atime_needs_update).