linux-kernel - [PATCH v2 1/1] xfrm: Use skb_mac_header_was_set() to check for MAC header presence

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Message-ID: <0490137bbc24e95eadf01bed9c31eb1d0a856a21.1693823464.git.sylv@sylv.io>
Date:   Mon,  4 Sep 2023 12:32:08 +0200
From:   Marcello Sylvester Bauer <email@...r.kernel.org>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     Marcello Sylvester Bauer <sylv@...v.io>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/1] xfrm: Use skb_mac_header_was_set() to check for MAC header presence

From: Marcello Sylvester Bauer <sylv@...v.io>

Add skb_mac_header_was_set() in xfrm4_remove_tunnel_encap() and
xfrm6_remove_tunnel_encap() to detect the presence of a MAC header.
This change prevents a kernel page fault on a non-zero mac_len when the
mac_header is not set.

Signed-off-by: Marcello Sylvester Bauer <sylv@...v.io>
---
 net/xfrm/xfrm_input.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index d5ee96789d4b..6d74bfa1e6e8 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -250,7 +250,7 @@ static int xfrm4_remove_tunnel_encap(struct xfrm_state *x, struct sk_buff *skb)

 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);
-	if (skb->mac_len)
+	if (skb->mac_len && skb_mac_header_was_set(skb))
 		eth_hdr(skb)->h_proto = skb->protocol;

 	err = 0;
@@ -287,7 +287,7 @@ static int xfrm6_remove_tunnel_encap(struct xfrm_state *x, struct sk_buff *skb)

 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);
-	if (skb->mac_len)
+	if (skb->mac_len && skb_mac_header_was_set(skb))
 		eth_hdr(skb)->h_proto = skb->protocol;

 	err = 0;
--
2.42.0