From a39f1a9a57a604bc55b2cd5d1ce08712e4508f15 Mon Sep 17 00:00:00 2001 From: Or Cohen Date: Thu, 3 Sep 2020 21:05:28 -0700 Subject: [PATCH 2068/2944] net/packet: fix overflow in tpacket_rcv fix #30547144 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 Signed-off-by: Eric Dumazet Signed-off-by: Linus Torvalds Signed-off-by: Tony Lu Acked-by: Dust Li --- net/packet/af_packet.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 7204e7b..85cd11b 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2153,7 +2153,8 @@ 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; @@ -2215,6 +2216,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, } macoff = netoff - maclen; } + if (netoff > USHRT_MAX) + goto drop_n_restore; if (po->tp_version <= TPACKET_V2) { if (macoff + snaplen > po->rx_ring.frame_size) { if (po->copy_thresh && -- 1.8.3.1