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Subject[PATCH 4.12 20/52] packet: Dont write vnet header beyond end of buffer
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Poirier <bpoirier@suse.com>


[ Upstream commit edbd58be15a957f6a760c4a514cd475217eb97fd ]

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

Fixes: 58d19b19cd99 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/packet/af_packet.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2192,6 +2192,7 @@ static int tpacket_rcv(struct sk_buff *s
struct timespec ts;
__u32 ts_status;
bool is_drop_n_account = false;
+ bool do_vnet = false;

/* 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
@@ -2242,8 +2243,10 @@ static int tpacket_rcv(struct sk_buff *s
netoff = TPACKET_ALIGN(po->tp_hdrlen +
(maclen < 16 ? 16 : maclen)) +
po->tp_reserve;
- if (po->has_vnet_hdr)
+ if (po->has_vnet_hdr) {
netoff += sizeof(struct virtio_net_hdr);
+ do_vnet = true;
+ }
macoff = netoff - maclen;
}
if (po->tp_version <= TPACKET_V2) {
@@ -2260,8 +2263,10 @@ static int tpacket_rcv(struct sk_buff *s
skb_set_owner_r(copy_skb, sk);
}
snaplen = po->rx_ring.frame_size - macoff;
- if ((int)snaplen < 0)
+ if ((int)snaplen < 0) {
snaplen = 0;
+ do_vnet = false;
+ }
}
} else if (unlikely(macoff + snaplen >
GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) {
@@ -2274,6 +2279,7 @@ static int tpacket_rcv(struct sk_buff *s
if (unlikely((int)snaplen < 0)) {
snaplen = 0;
macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len;
+ do_vnet = false;
}
}
spin_lock(&sk->sk_receive_queue.lock);
@@ -2299,7 +2305,7 @@ static int tpacket_rcv(struct sk_buff *s
}
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 -
sizeof(struct virtio_net_hdr),
vio_le(), true)) {

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