Commit acf69c94 authored Sep 03, 2020 by Or Cohen Committed by Linus Torvalds Sep 04, 2020

net/packet: fix overflow in tpacket_rcv



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: 8913336a ("packet: add PACKET_RESERVE sockopt")
Signed-off-by: Or Cohen <orcohen@paloaltonetworks.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b25d1dc9

net/packet/af_packet.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -2170,7 +2170,8 @@ 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 timespec64 ts;
		__u32 ts_status;
		@@ -2239,6 +2240,10 @@ static int tpacket_rcv(struct sk_buff skb, struct net_device dev,
		}
		macoff = netoff - maclen;
		}
		if (netoff > USHRT_MAX) {
		atomic_inc(&po->tp_drops);
		goto drop_n_restore;
		}
		if (po->tp_version <= TPACKET_V2) {
		if (macoff + snaplen > po->rx_ring.frame_size) {
		if (po->copy_thresh &&