From: Or Cohen <orcohen@paloaltonetworks.com>
Subject: net/packet: fix overflow in tpacket_rcv
Patch-mainline: Submitted - 2020-09-04 - 20200904040528.3635711-1-edumazet@google.com
References: CVE-2020-14386 bsc#1176069
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.
Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
Signed-off-by: Or Cohen <orcohen@paloaltonetworks.com>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
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
@@ -2198,7 +2198,8 @@ 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;
@@ -2260,6 +2261,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
}
macoff = netoff - maclen;
}
+ if (netoff > USHRT_MAX) {
+ po->stats.stats1.tp_drops++;
+ goto drop_n_restore;
+ }
if (po->tp_version <= TPACKET_V2) {
if (macoff + snaplen > po->rx_ring.frame_size) {
if (po->copy_thresh &&