netdev - [PATCH ipsec] xfrm: ipcomp: fix truesize computation on receive

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Message-ID: <f507d25958589ed4e6f62cdc4b8df64865865818.1745591479.git.sd@queasysnail.net>
Date: Fri, 25 Apr 2025 16:32:55 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: netdev@...r.kernel.org
Cc: Sabrina Dubroca <sd@...asysnail.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Steffen Klassert <steffen.klassert@...unet.com>
Subject: [PATCH ipsec] xfrm: ipcomp: fix truesize computation on receive

ipcomp_post_acomp currently drops all frags (via pskb_trim_unique(skb,
0)), and then subtracts the old skb->data_len from truesize. This
adjustment has already be done during trimming (in skb_condense), so
we don't need to do it again.

This shows up for example when running fragmented traffic over ipcomp,
we end up hitting the WARN_ON_ONCE in skb_try_coalesce.

Fixes: eb2953d26971 ("xfrm: ipcomp: Use crypto_acomp interface")
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 net/xfrm/xfrm_ipcomp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c
index 0c1420534394..907c3ccb440d 100644
--- a/net/xfrm/xfrm_ipcomp.c
+++ b/net/xfrm/xfrm_ipcomp.c
@@ -48,7 +48,6 @@ static int ipcomp_post_acomp(struct sk_buff *skb, int err, int hlen)
 {
 	struct acomp_req *req = ipcomp_cb(skb)->req;
 	struct ipcomp_req_extra *extra;
-	const int plen = skb->data_len;
 	struct scatterlist *dsg;
 	int len, dlen;
 
@@ -64,7 +63,7 @@ static int ipcomp_post_acomp(struct sk_buff *skb, int err, int hlen)
 
 	/* Only update truesize on input. */
 	if (!hlen)
-		skb->truesize += dlen - plen;
+		skb->truesize += dlen;
 	skb->data_len = dlen;
 	skb->len += dlen;
 
-- 
2.49.0