netdev - [PATCH v2] net: hsr: Use correct offset for HSR TLV values in supervisory HSR frames

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Message-Id: <20240228085644.3618044-1-lukma@denx.de>
Date: Wed, 28 Feb 2024 09:56:44 +0100
From: Lukasz Majewski <lukma@...x.de>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Andrew Lunn <andrew@...n.ch>,
	Eric Dumazet <edumazet@...gle.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	netdev@...r.kernel.org,
	Tristram.Ha@...rochip.com,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Lukasz Majewski <lukma@...x.de>
Subject: [PATCH v2] net: hsr: Use correct offset for HSR TLV values in supervisory HSR frames

Current HSR implementation uses following supervisory frame (even for
HSRv1 the HSR tag is not is not present):

00000000: 01 15 4e 00 01 2d XX YY ZZ 94 77 10 88 fb 00 01
00000010: 7e 1c 17 06 XX YY ZZ 94 77 10 1e 06 XX YY ZZ 94
00000020: 77 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00000030: 00 00 00 00 00 00 00 00 00 00 00 00

The current code adds extra two bytes (i.e. sizeof(struct hsr_sup_tlv))
when offset for skb_pull() is calculated.
This is wrong, as both 'struct hsrv1_ethhdr_sp' and 'hsrv0_ethhdr_sp'
already have 'struct hsr_sup_tag' defined in them, so there is no need
for adding extra two bytes.

This code was working correctly as with no RedBox support, the check for
HSR_TLV_EOT (0x00) was off by two bytes, which were corresponding to
zeroed padded bytes for minimal packet size.

Fixes: eafaa88b3eb7 ("net: hsr: Add support for redbox supervision frames")

Signed-off-by: Lukasz Majewski <lukma@...x.de>
---
Changes for v2:
- Update commit message to point to correct commit in "Fixes:"

---
 net/hsr/hsr_forward.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index 2afe28712a7a..5d68cb181695 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -83,7 +83,7 @@ static bool is_supervision_frame(struct hsr_priv *hsr, struct sk_buff *skb)
 		return false;
 
 	/* Get next tlv */
-	total_length += sizeof(struct hsr_sup_tlv) + hsr_sup_tag->tlv.HSR_TLV_length;
+	total_length += hsr_sup_tag->tlv.HSR_TLV_length;
 	if (!pskb_may_pull(skb, total_length))
 		return false;
 	skb_pull(skb, total_length);
-- 
2.20.1