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vxlan: use neigh_ha_snapshot() in route_shortcircuit()

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The neighbour hardware address n->ha can be updated asynchronously by the
neighbour subsystem, protected by n->ha_lock seqlock. Reading n->ha without
holding the seqlock loop can lead to torn reads or reading a partially updated
MAC address.

Use neigh_ha_snapshot() in route_shortcircuit() to safely copy n->ha under
read_seqbegin()/read_seqretry() lock protection before using it.

Note that arp_reduce() and neigh_reduce() seem to have the same issue
left for future patches.

Fixes: e4f67addf1 ("add DOVE extensions for VXLAN")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20260723144249.759100-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2026-07-23 14:42:47 +00:00
committed by Jakub Kicinski
parent 760d36e737
commit 8eca411347
1 changed files with 4 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/net/vxlan/vxlan_core.c
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@@ -2159,9 +2159,11 @@ static bool route_shortcircuit(struct net_device *dev, struct sk_buff *skb)
}
if (n) {
u8 haddr[ETH_ALEN];
bool diff;
diff = !ether_addr_equal(eth_hdr(skb)->h_dest, n->ha);
neigh_ha_snapshot(haddr, n, dev);
diff = !ether_addr_equal_unaligned(eth_hdr(skb)->h_dest, haddr);
if (diff) {
if (skb_cow_head(skb, 0)) {
neigh_release(n);
@@ -2169,7 +2171,7 @@ static bool route_shortcircuit(struct net_device *dev, struct sk_buff *skb)
}
memcpy(eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest,
dev->addr_len);
memcpy(eth_hdr(skb)->h_dest, n->ha, dev->addr_len);
memcpy(eth_hdr(skb)->h_dest, haddr, dev->addr_len);
}
neigh_release(n);
return diff;