netdev - Re: [PATCH] macsec: avoid heap overflow in skb_to

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Message-ID: <20170425151248.GB25241@bistromath.localdomain>
Date:   Tue, 25 Apr 2017 17:12:48 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Miller <davem@...emloft.net>, stable@...r.kernel.org,
        security@...nel.org
Subject: Re: [PATCH] macsec: avoid heap overflow in skb_to_sgvec

2017-04-25, 17:08:28 +0200, Jason A. Donenfeld wrote:
> Hi Sabrina,
> 
> On Tue, Apr 25, 2017 at 4:53 PM, Sabrina Dubroca <sd@...asysnail.net> wrote:
> > Ugh, good catch :/
> >
> > AFAICT this patch doesn't really help, because NETIF_F_FRAGLIST
> > doesn't get tested in paths that can lead to triggering this.
> 
> You're right. This fixes the xmit() path, but not the receive path,
> which appears to take skbs directly from the upper device.
> 
> > I'll post a patch to allocate a properly-sized sg array.
> 
> I just posted this series, which should fix things in a robust way:
> 
> https://patchwork.ozlabs.org/patch/754861/

Yes, that prevents the overflow, but now you're just dropping
packets. I'll review that later, let's fix the overflow without
breaking connectivity for now.

-- 
Sabrina