From: Or Cohen orcohen@paloaltonetworks.com
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 orcohen@paloaltonetworks.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ snu: backported to pre-5.3, changed tp_drops counting/locking ] Signed-off-by: Stefan Nuernberger snu@amazon.com CC: David Woodhouse dwmw@amazon.co.uk CC: Amit Shah aams@amazon.com CC: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/packet/af_packet.c | 9 ++++++++- 1 file changed, 8 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 &&