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

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

[Sabrina Dubroca]

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@queasysnail.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

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

[Herbert Xu]

On Fri, Apr 25, 2025 at 04:32:55PM +0200, Sabrina Dubroca wrote:
> 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@queasysnail.net>
> ---
>  net/xfrm/xfrm_ipcomp.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)

Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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

[Steffen Klassert]

On Fri, Apr 25, 2025 at 04:32:55PM +0200, Sabrina Dubroca wrote:
> 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@queasysnail.net>

Patch applied, thanks Sabrina!