[PATCH v2 net] net-gro: reset skb->pkt_type in napi_reuse_skb()

[PATCH v2 net] net-gro: reset skb->pkt_type in napi_reuse_skb()

[Eric Dumazet]

eth_type_trans() assumes initial value for skb->pkt_type
is PACKET_HOST.

This is indeed the value right after a fresh skb allocation.

However, it is possible that GRO merged a packet with a different
value (like PACKET_OTHERHOST in case macvlan is used), so
we need to make sure napi->skb will have pkt_type set back to
PACKET_HOST.

Otherwise, valid packets might be dropped by the stack because
their pkt_type is not PACKET_HOST.

napi_reuse_skb() was added in commit 96e93eab2033 ("gro: Add
internal interfaces for VLAN"), but this bug always has
been there.

Fixes: 96e93eab2033 ("gro: Add internal interfaces for VLAN")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 0ffcbdd55fa9ee545c807f2ed3fc178830e3075a..066aa902d85c3e3f5ad83244b1506a446bebcb88 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5655,6 +5655,10 @@ static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
 	skb->vlan_tci = 0;
 	skb->dev = napi->dev;
 	skb->skb_iif = 0;
+
+	/* eth_type_trans() assumes pkt_type is PACKET_HOST */
+	skb->pkt_type = PACKET_HOST;
+
 	skb->encapsulation = 0;
 	skb_shinfo(skb)->gso_type = 0;
 	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
-- 
2.19.1.1215.g8438c0b245-goog

Re: [PATCH v2 net] net-gro: reset skb->pkt_type in napi_reuse_skb()

[David Miller]

From: Eric Dumazet <edumazet@google.com>
Date: Sat, 17 Nov 2018 21:57:02 -0800

> eth_type_trans() assumes initial value for skb->pkt_type
> is PACKET_HOST.
> 
> This is indeed the value right after a fresh skb allocation.
> 
> However, it is possible that GRO merged a packet with a different
> value (like PACKET_OTHERHOST in case macvlan is used), so
> we need to make sure napi->skb will have pkt_type set back to
> PACKET_HOST.
> 
> Otherwise, valid packets might be dropped by the stack because
> their pkt_type is not PACKET_HOST.
> 
> napi_reuse_skb() was added in commit 96e93eab2033 ("gro: Add
> internal interfaces for VLAN"), but this bug always has
> been there.
> 
> Fixes: 96e93eab2033 ("gro: Add internal interfaces for VLAN")
> Signed-off-by: Eric Dumazet <edumazet@google.com>

I was wondering about that WARN_ON in v1 :-)

Applied and queued up for -stable.