Re: [PATCH] packet: Don't write vnet header beyond end of buffer

[David Miller]

From: Benjamin Poirier 
Date: Mon, 28 Aug 2017 14:29:41 -0400

> ... 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 
> Cc: Willem de Bruijn 

Applied and queued up for -stable.

Re: [PATCH] packet: Don't write vnet header beyond end of buffer

[Willem de Bruijn]

On Mon, Aug 28, 2017 at 2:29 PM, Benjamin Poirier  wrote:
> ... 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 
> Cc: Willem de Bruijn 

Acked-by: Willem de Bruijn 

Thanks for fixing this, Benjamin.

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

[Benjamin Poirier]

... 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 
Cc: Willem de Bruijn 
---
 net/packet/af_packet.c | 12 +---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 008a45ca3112..1c61af9af67d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2191,6 +2191,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct 
net_device *dev,
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
@@ -2241,8 +2242,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct 
net_device *dev,
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) {
@@ -2259,8 +2262,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct 
net_device *dev,
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(>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)) {
snaplen = 0;
macoff = GET_PBDQC_FROM_RB(>rx_ring)->max_frame_len;
+   do_vnet = false;
}
}
spin_lock(>sk_receive_queue.lock);
@@ -2298,7 +2304,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct 
net_device *dev,
}
spin_unlock(>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)) {
-- 
2.14.1