netdev - Re: [PATCH] net/packet: fix overflow in tpacket

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Date:   Sat, 5 Sep 2020 08:54:22 +0200
From:   Salvatore Bonaccorso <carnil@...ian.org>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc:     "Nuernberger, Stefan" <snu@...zon.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "orcohen@...oaltonetworks.com" <orcohen@...oaltonetworks.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "Shah, Amit" <aams@...zon.de>
Subject: Re: [PATCH] net/packet: fix overflow in tpacket_rcv

Hi,

On Fri, Sep 04, 2020 at 04:36:48PM +0200, gregkh@...uxfoundation.org wrote:
> On Fri, Sep 04, 2020 at 02:22:46PM +0000, Nuernberger, Stefan wrote:
> > On Fri, 2020-09-04 at 16:16 +0200, Greg Kroah-Hartman wrote:
> > > On Fri, Sep 04, 2020 at 03:30:52PM +0200, Stefan Nuernberger wrote:
> > > > 
> > > > From: Or Cohen <orcohen@...oaltonetworks.com>
> > > > 
> > > > Using tp_reserve to calculate netoff can overflow as
> > > > tp_reserve is unsigned int and netoff is unsigned short.
> > > > 
> > > > This may lead to macoff receving a smaller value then
> > > > sizeof(struct virtio_net_hdr), and if po->has_vnet_hdr
> > > > is set, an out-of-bounds write will occur when
> > > > calling virtio_net_hdr_from_skb.
> > > > 
> > > > The bug is fixed by converting netoff to unsigned int
> > > > and checking if it exceeds USHRT_MAX.
> > > > 
> > > > This addresses CVE-2020-14386
> > > > 
> > > > Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
> > > > Signed-off-by: Or Cohen <orcohen@...oaltonetworks.com>
> > > > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > > > 
> > > > [ snu: backported to 4.9, changed tp_drops counting/locking ]
> > > > 
> > > > Signed-off-by: Stefan Nuernberger <snu@...zon.com>
> > > > CC: David Woodhouse <dwmw@...zon.co.uk>
> > > > CC: Amit Shah <aams@...zon.com>
> > > > CC: stable@...r.kernel.org
> > > > ---
> > > >  net/packet/af_packet.c | 9 ++++++++-
> > > >  1 file changed, 8 insertions(+), 1 deletion(-)
> > > What is the git commit id of this patch in Linus's tree?
> > > 
> > 
> > Sorry, this isn't merged on Linus' tree yet. It's a heads up that the
> > backport isn't straightforward.
> 
> Ok, please be more specific about this when sending patches out...

The commit is in Linux' tree now as
acf69c946233259ab4d64f8869d4037a198c7f06 .

Older stable series, which do not have 8e8e2951e309 ("net/packet: make
tp_drops atomic") will though need a backport as per above AFICS.

Regards,
Salvatore