* [PATCH net] net/packet: fix overflow in tpacket_rcv
@ 2020-09-04 4:05 Eric Dumazet
0 siblings, 0 replies; only message in thread
From: Eric Dumazet @ 2020-09-04 4:05 UTC (permalink / raw)
To: David S . Miller
Cc: netdev, Eric Dumazet, Linus Torvalds, Eric Dumazet, Or Cohen
From: Or Cohen <orcohen@paloaltonetworks.com>
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 <orcohen@paloaltonetworks.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/packet/af_packet.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 479c257ded7335616da35aa5f7880b54aa2f9fe0..1377a485d45109da8e5f241ff8f64d4f37180592 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -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 &&
--
2.28.0.526.ge36021eeef-goog
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