From 97d7817dcebb5857a7b54af40b7edf4134433f13 Mon Sep 17 00:00:00 2001 From: Or Cohen Date: Thu, 3 Sep 2020 21:05:28 -0700 Subject: [PATCH] net/packet: fix overflow in tpacket_rcv 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 [ snu: backported to pre-5.3, changed tp_drops counting/locking ] Signed-off-by: Stefan Nuernberger CC: David Woodhouse CC: Amit Shah CC: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Change-Id: Id70a19d5550c27f8527f95b2a838d53e3bb73ffb --- 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 ebc15b0ae922..e5239b7fc5fd 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1753,7 +1753,8 @@ 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; @@ -1800,6 +1801,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, po->tp_reserve; 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 &&