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

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-prev] [day] [month] [year] [list]

Message-ID: <20200921170250.28535-1-snu@amazon.com>
Date:   Mon, 21 Sep 2020 19:02:50 +0200
From:   Stefan Nuernberger <snu@...zon.com>
To:     <carnil@...ian.org>
CC:     <aams@...zon.de>, <dwmw@...zon.co.uk>, <edumazet@...gle.com>,
        <gregkh@...uxfoundation.org>, <netdev@...r.kernel.org>,
        <orcohen@...oaltonetworks.com>, <snu@...zon.de>,
        <stable@...r.kernel.org>, Stefan Nuernberger <snu@...zon.com>,
        Amit Shah <aams@...zon.com>
Subject: [PATCH] net/packet: fix overflow in tpacket_rcv

From: Or Cohen <orcohen@...oaltonetworks.com>

commit acf69c946233259ab4d64f8869d4037a198c7f06 upstream.

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 pre-5.3, 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(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index fb643945e424..b5b79f501541 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2161,7 +2161,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	int skb_len = skb->len;
 	unsigned int snaplen, res;
 	unsigned long status = TP_STATUS_USER;
-	unsigned short macoff, netoff, hdrlen;
+	unsigned short macoff, hdrlen;
+	unsigned int netoff;
 	struct sk_buff *copy_skb = NULL;
 	struct timespec ts;
 	__u32 ts_status;
@@ -2223,6 +2224,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		}
 		macoff = netoff - maclen;
 	}
+	if (netoff > USHRT_MAX) {
+		spin_lock(&sk->sk_receive_queue.lock);
+		po->stats.stats1.tp_drops++;
+		spin_unlock(&sk->sk_receive_queue.lock);
+		goto drop_n_restore;
+	}
 	if (po->tp_version <= TPACKET_V2) {
 		if (macoff + snaplen > po->rx_ring.frame_size) {
 			if (po->copy_thresh &&
-- 
2.28.0




Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879