netdev - [PATCH net] xfrm: Linearize the skb after offloading if needed.

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Message-ID: <20230614100202.1-YtK7H5@linutronix.de>
Date: Wed, 14 Jun 2023 12:02:02 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH net] xfrm: Linearize the skb after offloading if needed.

With offloading enabled, esp_xmit() gets invoked very late, from within
validate_xmit_xfrm() which is after validate_xmit_skb() validates and
linearizes the skb if the underlying device does not support fragments.

esp_output_tail() may add a fragment to the skb while adding the auth
tag/ IV. Devices without the proper support will then send skb->data
points to with the correct length so the packet will have garbage at the
end. A pcap sniffer will claim that the proper data has been sent since
it parses the skb properly.

It is not affected with INET_ESP_OFFLOAD disabled.

Linearize the skb after offloading if the sending hardware requires it.
It was tested on v4, v6 has been adopted.

Fixes: 7785bba299a8d ("esp: Add a software GRO codepath")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 net/ipv4/esp4_offload.c | 3 +++
 net/ipv6/esp6_offload.c | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index 3969fa805679c..ee848be59e65a 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -340,6 +340,9 @@ static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_
 
 	secpath_reset(skb);
 
+	if (skb_needs_linearize(skb, skb->dev->features) &&
+	    __skb_linearize(skb))
+		return -ENOMEM;
 	return 0;
 }
 
diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index 75c02992c520f..7723402689973 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c
@@ -374,6 +374,9 @@ static int esp6_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features
 
 	secpath_reset(skb);
 
+	if (skb_needs_linearize(skb, skb->dev->features) &&
+	    __skb_linearize(skb))
+		return -ENOMEM;
 	return 0;
 }
 
-- 
2.40.1