From: Eric Dumazet <edumazet@xxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
[ Upstream commit 2f1d8b9e8afa5a833d96afcd23abcb8cdf8d83ab ]
Brian reported crashes using IPv6 traffic with macvtap/veth combo.
I tracked the crashes in neigh_hh_output()
-> memcpy(skb->data - HH_DATA_MOD, hh->hh_data, HH_DATA_MOD);
Neighbour code assumes headroom to push Ethernet header is
at least 16 bytes.
It appears macvtap has only 14 bytes available on arches
where NET_IP_ALIGN is 0 (like x86)
Effect is a corruption of 2 bytes right before skb->head,
and possible crashes if accessing non existing memory.
This fix should also increase IPv4 performance, as paranoid code
in ip_finish_output2() wont have to call skb_realloc_headroom()
Reported-by: Brian Rak <brak@xxxxxxxxx>
Tested-by: Brian Rak <brak@xxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
drivers/net/macvtap.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 89d21fc47a16..393873fb792e 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -635,12 +635,15 @@ static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
return 0;
}
+/* Neighbour code has some assumptions on HH_DATA_MOD alignment */
+#define MACVTAP_RESERVE HH_DATA_OFF(ETH_HLEN)
+
/* Get packet from user space buffer */
static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
const struct iovec *iv, unsigned long total_len,
size_t count, int noblock)
{
- int good_linear = SKB_MAX_HEAD(NET_IP_ALIGN);
+ int good_linear = SKB_MAX_HEAD(MACVTAP_RESERVE);
struct sk_buff *skb;
struct macvlan_dev *vlan;
unsigned long len = total_len;
@@ -699,7 +702,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
linear = vnet_hdr.hdr_len;
}
- skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen,
+ skb = macvtap_alloc_skb(&q->sk, MACVTAP_RESERVE, copylen,
linear, noblock, &err);
if (!skb)
goto err;
--
2.3.0
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