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packet: Don't write vnet header beyond end of buffer

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... which may happen with certain values of tp_reserve and maclen.

Fixes: 58d19b19cd ("packet: vnet_hdr support for tpacket_rcv")
Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Benjamin Poirier 2017-08-28 14:29:41 -04:00 committed by David S. Miller
parent d55c60eba0
commit edbd58be15
1 changed files with 9 additions and 3 deletions
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12
net/packet/af_packet.c
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@ -2191,6 +2191,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
struct timespec ts; struct timespec ts;
__u32 ts_status; __u32 ts_status;
bool is_drop_n_account = false; bool is_drop_n_account = false;
bool do_vnet = false;
/* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT. /* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
* We may add members to them until current aligned size without forcing * We may add members to them until current aligned size without forcing
@ -2241,8 +2242,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
netoff = TPACKET_ALIGN(po->tp_hdrlen + netoff = TPACKET_ALIGN(po->tp_hdrlen +
(maclen < 16 ? 16 : maclen)) + (maclen < 16 ? 16 : maclen)) +
po->tp_reserve; po->tp_reserve;
if (po->has_vnet_hdr) if (po->has_vnet_hdr) {
netoff += sizeof(struct virtio_net_hdr); netoff += sizeof(struct virtio_net_hdr);
do_vnet = true;
}
macoff = netoff - maclen; macoff = netoff - maclen;
} }
if (po->tp_version <= TPACKET_V2) { if (po->tp_version <= TPACKET_V2) {
@ -2259,8 +2262,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
skb_set_owner_r(copy_skb, sk); skb_set_owner_r(copy_skb, sk);
} }
snaplen = po->rx_ring.frame_size - macoff; snaplen = po->rx_ring.frame_size - macoff;
if ((int)snaplen < 0) if ((int)snaplen < 0) {
snaplen = 0; snaplen = 0;
do_vnet = false;
}
} }
} else if (unlikely(macoff + snaplen > } else if (unlikely(macoff + snaplen >
GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) { GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) {
@ -2273,6 +2278,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
if (unlikely((int)snaplen < 0)) { if (unlikely((int)snaplen < 0)) {
snaplen = 0; snaplen = 0;
macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len; macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len;
do_vnet = false;
} }
} }
spin_lock(&sk->sk_receive_queue.lock); spin_lock(&sk->sk_receive_queue.lock);
@ -2298,7 +2304,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
} }
spin_unlock(&sk->sk_receive_queue.lock); spin_unlock(&sk->sk_receive_queue.lock);
if (po->has_vnet_hdr) { if (do_vnet) {
if (virtio_net_hdr_from_skb(skb, h.raw + macoff - if (virtio_net_hdr_from_skb(skb, h.raw + macoff -
sizeof(struct virtio_net_hdr), sizeof(struct virtio_net_hdr),
vio_le(), true)) { vio_le(), true)) {