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[2a01:cb05:8918:ce00:dd1a:5a4f:9908:f2d5]) by smtp.gmail.com with ESMTPSA id t17sm9686329wru.94.2021.08.06.08.52.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Aug 2021 08:52:08 -0700 (PDT) Date: Fri, 6 Aug 2021 17:52:06 +0200 From: Guillaume Nault To: David Miller , Jakub Kicinski Cc: netdev@vger.kernel.org, Martin Varghese , Willem de Bruijn Subject: [PATCH net] bareudp: Fix invalid read beyond skb's linear data Message-ID: <7741c46545c6ef02e70c80a9b32814b22d9616b3.1628264975.git.gnault@redhat.com> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- 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))) { + bareudp->dev->stats.rx_dropped++; + goto drop; + } + ipversion >>= 4; + + if (ipversion == 4) { + proto = htons(ETH_P_IP); + } else if (ipversion == 6 && bareudp->multi_proto_mode) { proto = htons(ETH_P_IPV6); } else { bareudp->dev->stats.rx_dropped++;