From: Andrei Vagin <avagin@virtuozzo.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
linux-kernel@vger.kernel.org, xemul@virtuozzo.com
Subject: Re: proc: fix /proc/*/map_files lookup
Date: Wed, 29 Nov 2017 15:23:42 -0800 [thread overview]
Message-ID: <20171129232341.GA32749@outlook.office365.com> (raw)
In-Reply-To: <20171129145603.3adf4f0ba2bc9d4a4698d552@linux-foundation.org>
On Wed, Nov 29, 2017 at 02:56:03PM -0800, Andrew Morton wrote:
> On Mon, 27 Nov 2017 21:29:25 -0800 Andrei Vagin <avagin@virtuozzo.com> wrote:
>
> > On Tue, Nov 21, 2017 at 12:27:06AM +0300, Alexey Dobriyan wrote:
> > > Current code does:
> > >
> > > if (sscanf(dentry->d_name.name, "%lx-%lx", start, end) != 2)
> > >
> > > However sscanf() is broken garbage.
> > >
> > > It silently accepts whitespace between format specifiers
> > > (did you know that?).
> > >
> > > It silently accepts valid strings which result in integer overflow.
> > >
> > > Do not use sscanf() for any even remotely reliable parsing code.
> >
> > This patch breaks criu, criu has one places where a file name is generated
> > as map_files/%p-%p
> >
> > openat(1048572, "map_files/0x7f9912dd5000-0x7f9912de4000", O_RDWR) = -1 ENOENT (No such file or directory) <0.000015>
> >
> > And this code worked before this patch and it doesn't work with this
> > patch. And you have to know that we never break user-space programs ;)
> >
> > But seriously, the patch looks good to me, but I would prefer to not queue
> > it into stable kernels.
>
> The patch breaks CRIU but you're OK with merging it? How does that work ;)
It was a bug in criu. And this bug is on a minor path, which works when
memfd_create() isn't available. It is a reason why I ask to not
backport this patch to stable kernels.
In CRIU this bug can be triggered, only if this patch will be backported
to a kernel which version is lower than v3.16.
>
> Now I'm worried that it will break other things.
I think a chance is very small. All programs should use names which
listed in /proc/PID/map_files/.
prev parent reply other threads:[~2017-11-29 23:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-20 21:27 [PATCH] proc: fix /proc/*/map_files lookup Alexey Dobriyan
2017-11-20 22:16 ` Andrew Morton
2017-11-21 5:48 ` Alexey Dobriyan
2017-11-28 5:29 ` Andrei Vagin
2017-11-28 10:12 ` Alexey Dobriyan
2017-11-29 22:56 ` Andrew Morton
2017-11-29 23:23 ` Andrei Vagin [this message]
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