netdev - Re: [devel-ipsec] Re: [PATCH ipsec-next 4/6] xfrm: add XFRM_MSG_MIGRATE

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Message-ID: <aWoatI4v84lJAC48@Antony2201.local>
Date: Fri, 16 Jan 2026 12:02:12 +0100
From: Antony Antony <antony@...nome.org>
To: Simon Horman <horms@...nel.org>
Cc: Antony Antony <antony@...nome.org>,
	Antony Antony <antony.antony@...unet.com>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Herbert Xu <herbert@...dor.apana.org.au>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	devel@...ux-ipsec.org
Subject: Re: [devel-ipsec] Re: [PATCH ipsec-next 4/6] xfrm: add
 XFRM_MSG_MIGRATE_STATE for single SA migration

On Thu, Jan 15, 2026 at 01:44:50PM +0000, Simon Horman via Devel wrote:
> On Wed, Jan 14, 2026 at 05:09:20PM +0100, Antony Antony wrote:
> 
> Hi Antony,
> 
> > Hi Simon,
> > 
> > On Tue, Jan 13, 2026 at 02:57:16PM +0000, Simon Horman via Devel wrote:
> > > On Fri, Jan 09, 2026 at 02:38:05PM +0100, Antony Antony wrote:
> 
> ...
> 
> > > > +static int xfrm_send_migrate_state(const struct xfrm_user_migrate_state *um,
> > > > +				   const struct xfrm_encap_tmpl *encap,
> > > > +				   const struct xfrm_user_offload *xuo)
> > > > +{
> > > > +	int err;
> > > > +	struct sk_buff *skb;
> > > > +	struct net *net = &init_net;
> > > > +
> > > > +	skb = nlmsg_new(xfrm_migrate_state_msgsize(!!encap, !!xuo), GFP_ATOMIC);
> > > > +	if (!skb)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	err = build_migrate_state(skb, um, encap, xuo);
> > > > +	if (err < 0) {
> > > > +		WARN_ON(1);

kfree_skb(skb); replace the above line; explained bellow

> > > > +		return err;
> > > 
> > > skb seems to be leaked here.
> > > 
> > > Also flagged by Review Prompts.
> > 
> > I don't see a skb leak. It also looks similar to the functions above.
> 
> xfrm_get_ae() is the previous caller of nlmsg_new() in this file.
> It calls BUG_ON() on error, so leaking is not an issue there.
> 
> The caller before that is xfrm_get_default() which calls kfree_skb() in
> it's error path. Maybe I'm missing something obvious, but I was thinking
> that approach is appropriate here too.

You’re right. There is a leak in the error path.

The new helper I added is similar to build_migrate(), but that code uses
BUG_ON() on the error path. That feels too extreme here (even though there
are other instances of it in the same file).

I’ll follow the pattern in xfrm_get_default(): handle the error by freeing
the skb (kfree_skb()) and returning an error. And no WARN_ON().

I’ll send v3 shortly.

thanks,
-antony