From: Or Cohen Date: Thu, 3 Sep 2020 21:05:28 -0700 Subject: net/packet: fix overflow in tpacket_rcv Origin: https://git.kernel.org/linus/acf69c946233259ab4d64f8869d4037a198c7f06 Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2020-14386 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 [Salvatore Bonaccorso: Backport to v4.19.y: - Adjust for context changes - Revert change to use atomic_inc as v4.19.y does not contain 8e8e2951e309 ("net/packet: make tp_drops atomic") introduced in v5.3-rc1 ] --- net/packet/af_packet.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2162,7 +2162,8 @@ static int tpacket_rcv(struct sk_buff *s 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; @@ -2225,6 +2226,12 @@ static int tpacket_rcv(struct sk_buff *s } 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 &&