netdev - [PATCH net] bareudp: Fix invalid read beyond skb's linear data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 6 Aug 2021 17:52:06 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org,
        Martin Varghese <martin.varghese@...ia.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net] bareudp: Fix invalid read beyond skb's linear data

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@...hat.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))) {
+			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++;
-- 
2.21.3