From: Guillaume Nault <gnault@redhat.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: David Miller <davem@davemloft.net>,
netdev@vger.kernel.org,
Martin Varghese <martin.varghese@nokia.com>,
Willem de Bruijn <willemb@google.com>
Subject: Re: [PATCH net] bareudp: Fix invalid read beyond skb's linear data
Date: Sun, 8 Aug 2021 18:16:25 +0200 [thread overview]
Message-ID: <20210808161625.GA2912@pc-32.home> (raw)
In-Reply-To: <20210806162234.69334902@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
On Fri, Aug 06, 2021 at 04:22:34PM -0700, Jakub Kicinski wrote:
> On Fri, 6 Aug 2021 17:52:06 +0200 Guillaume Nault wrote:
> > Data beyond the UDP header might not be part of the skb's linear data.
> > Use skb_copy_bits() instead of direct access to skb->data+X, so that
> > we read the correct bytes even on a fragmented skb.
> >
> > Fixes: 4b5f67232d95 ("net: Special handling for IP & MPLS.")
> > Signed-off-by: Guillaume Nault <gnault@redhat.com>
> > ---
> > drivers/net/bareudp.c | 16 +++++++++++-----
> > 1 file changed, 11 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
> > index a7ee0af1af90..54e321a695ce 100644
> > --- a/drivers/net/bareudp.c
> > +++ b/drivers/net/bareudp.c
> > @@ -71,12 +71,18 @@ static int bareudp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
> > family = AF_INET6;
> >
> > if (bareudp->ethertype == htons(ETH_P_IP)) {
> > - struct iphdr *iphdr;
> > + __u8 ipversion;
> >
> > - iphdr = (struct iphdr *)(skb->data + BAREUDP_BASE_HLEN);
> > - if (iphdr->version == 4) {
> > - proto = bareudp->ethertype;
> > - } else if (bareudp->multi_proto_mode && (iphdr->version == 6)) {
> > + if (skb_copy_bits(skb, BAREUDP_BASE_HLEN, &ipversion,
> > + sizeof(ipversion))) {
>
> No preference just curious - could skb_header_pointer() be better suited?
I have no preference either. I just used skb_copy_bits() because it
didn't seem useful to get a pointer to the buffer (just to read one
byte of data).
But I don't mind reposting with skb_header_pointer() if anyone prefers
that solution.
next prev parent reply other threads:[~2021-08-08 16:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-06 15:52 [PATCH net] bareudp: Fix invalid read beyond skb's linear data Guillaume Nault
2021-08-06 23:22 ` Jakub Kicinski
2021-08-08 16:16 ` Guillaume Nault [this message]
2021-08-09 16:19 ` Jakub Kicinski
2021-08-10 9:33 ` Guillaume Nault
2021-08-09 22:40 ` patchwork-bot+netdevbpf
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