From: Florian Westphal <fw@xxxxxxxxx>
commit 6a7ac3d20593865209dceb554d8b3f094c6bd940 upstream.
If we try to emit an icmp error in response to a nonliner skb, we get
BUG: KASAN: slab-out-of-bounds in ip_compute_csum+0x134/0x220
Read of size 4 at addr ffff88811c50db00 by task iperf3/1691
CPU: 2 PID: 1691 Comm: iperf3 Not tainted 6.5.0-rc3+ #309
[..]
kasan_report+0x105/0x140
ip_compute_csum+0x134/0x220
iptunnel_pmtud_build_icmp+0x554/0x1020
skb_tunnel_check_pmtu+0x513/0xb80
vxlan_xmit_one+0x139e/0x2ef0
vxlan_xmit+0x1867/0x2760
dev_hard_start_xmit+0x1ee/0x4f0
br_dev_queue_push_xmit+0x4d1/0x660
[..]
ip_compute_csum() cannot deal with nonlinear skbs, so avoid it.
After this change, splat is gone and iperf3 is no longer stuck.
Fixes: 4cb47a8644cc ("tunnels: PMTU discovery support for directly bridged IP packets")
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230803152653.29535-2-fw@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/ip_tunnel_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -224,7 +224,7 @@ static int iptunnel_pmtud_build_icmp(str
.un.frag.__unused = 0,
.un.frag.mtu = htons(mtu),
};
- icmph->checksum = ip_compute_csum(icmph, len);
+ icmph->checksum = csum_fold(skb_checksum(skb, 0, len, 0));
skb_reset_transport_header(skb);
niph = skb_push(skb, sizeof(*niph));
