net/packet: fix overflow in tpacket_rcv
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.
BUG=b/167730744
TEST=Manually tried the reproducer before and after this fix.
RELEASE_NOTE=Fixed overflow in tpacket_rcv, which caused
CVE-2020-14386.
SOURCE=FROMLIST(https://www.openwall.com/lists/oss-security/2020/09/03/3)
Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
Signed-off-by: Or Cohen <orcohen@paloaltonetworks.com>
Signed-off-by: Roy Yang <royyang@google.com>
Change-Id: I119b9e950f948259bbf0e3afeda5f33c0fb40e51
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/4981
Reviewed-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 7735340..fbc2d4d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2169,7 +2169,8 @@
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;
@@ -2238,6 +2239,10 @@
}
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 &&
