[PATCH net-next v4 03/12] geneve: Fix off-by-one comparing with GRO_LEGACY_MAX_SIZE

[Alice Mikityanska <alice.kernel@fastmail.im>]

From: Alice Mikityanska <alice@isovalent.com>

GRO_LEGACY_MAX_SIZE = 65536; total_len being 65536 is too big to fit
into a u16. As can be seen in skb_gro_receive, packets bigger or equal
to gro_max_size (or GRO_LEGACY_MAX_SIZE) are dropped with -E2BIG. Apply
the same boundary to geneve_post_decap_hint to avoid writing 65536 to a
16-bit iph->tot_len field with an overflow.

Fixes: fd0dd796576e ("geneve: use GRO hint option in the RX path")
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
 drivers/net/geneve.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index b36fad833724..aee05be69d1e 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -603,7 +603,7 @@ static int geneve_post_decap_hint(const struct sock *sk, struct sk_buff *skb,
 	ipv6h = (void *)skb->data + gro_hint->nested_nh_offset;
 	iph = (struct iphdr *)ipv6h;
 	total_len = skb->len - gro_hint->nested_nh_offset;
-	if (total_len > GRO_LEGACY_MAX_SIZE)
+	if (total_len >= GRO_LEGACY_MAX_SIZE)
 		return -E2BIG;
 
 	/*
-- 
2.54.0