netdev - Re: net/xfrm: stack out-of-bounds in xfrm_flowi

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Message-ID: <20170214090816.GJ30338@gauss.secunet.com>
Date:   Tue, 14 Feb 2017 10:08:16 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/xfrm: stack out-of-bounds in xfrm_flowi_sport

On Tue, Feb 14, 2017 at 09:41:35AM +0100, Dmitry Vyukov wrote:
> On Tue, Feb 14, 2017 at 8:08 AM, Steffen Klassert
> <steffen.klassert@...unet.com> wrote:
> > On Mon, Feb 13, 2017 at 03:46:56PM +0100, Dmitry Vyukov wrote:
> >>
> >> On commit 7089db84e356562f8ba737c29e472cc42d530dbc.
> >>
> >>
> >> struct flowi4 fl4_stack allocated on stack in udp_sendmsg is being
> >> casted to larger struct flowi and then accessed.
> >
> > Looks like the problem is when using IPv4-mapped IPv6 addresses.
> >
> > Does the patch below help?
> 
> 
> Steffen, can you please run the reproducer I provided?
> I specifically spent time to supply you with a simple, reliable
> reproducer. I am not even saying about adding a test case for the bug.
> Kernel development practices seem to encourage developers to not
> bother with tests. But at least testing a patch that you are sending
> looks like a reasonable thing to do.

I tested this with my socket policy testcases of course.
I dont have a IPv4-mapped IPv6 addresses testcase and
changing userspace in my test setup means to rebuild
the system iso image.

Asking for a test is not so uncommon. You have the
testcase, why not running it again?