netdev - [PATCH net] net: Clear old fragment checksum value in napi_get

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Message-ID: <20250221161405.1921296-1-mheib@redhat.com>
Date: Fri, 21 Feb 2025 18:14:05 +0200
From: Mohammad Heib <mheib@...hat.com>
To: netdev@...r.kernel.org
Cc: Mohammad Heib <mheib@...hat.com>
Subject: [PATCH net] net: Clear old fragment checksum value in napi_get_frags

In certain cases, napi_get_frags() returns an skb that points to an old
received fragment, This skb may have its skb->ip_summed, csum, and other
fields set from previous fragment handling.

Some network drivers set skb->ip_summed to either CHECKSUM_COMPLETE or
CHECKSUM_UNNECESSARY when getting skb from napi_get_frags(), while
others only set skb->ip_summed when RX checksum offload is enabled on
the device, and do not set any value for skb->ip_summed when hardware
checksum offload is disabled, assuming that the skb->ip_summed
initiated to zero by napi_get_frags.

This inconsistency sometimes leads to checksum validation issues in the
upper layers of the network stack.

To resolve this, this patch clears the skb->ip_summed value for each skb
returned by napi_get_frags(), ensuring that the caller is responsible
for setting the correct checksum status. This eliminates potential
checksum validation issues caused by improper handling of
skb->ip_summed.

Fixes: 76620aafd66f ("gro: New frags interface to avoid copying shinfo")
Signed-off-by: Mohammad Heib <mheib@...hat.com>
---
 net/core/gro.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/gro.c b/net/core/gro.c
index 78b320b63174..e98007d8f26f 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -675,6 +675,8 @@ struct sk_buff *napi_get_frags(struct napi_struct *napi)
 			napi->skb = skb;
 			skb_mark_napi_id(skb, napi);
 		}
+	} else {
+		skb->ip_summed = CHECKSUM_NONE;
 	}
 	return skb;
 }
-- 
2.48.1