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Date:   Wed, 02 Nov 2022 08:05:00 -0700
From:   Kees Cook <kees@kernel.org>
To:     Tao Chen <chentao.kernel@linux.alibaba.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        Oliver Hartkopp <socketcan@hartkopp.net>,
        Petr Machata <petrm@nvidia.com>,
        Kees Cook <keescook@chromium.org>,
        Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
CC:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_net-next=5D_netlink=3A_Fix_p?= =?US-ASCII?Q?otential_skb_memleak_in_netlink=5Fack?=
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On November 2, 2022 5:08:20 AM PDT, Tao Chen <chentao=2Ekernel@linux=2Ealib=
aba=2Ecom> wrote:
>We should clean the skb resource if nlmsg_put/append failed
>, so fix it=2E
>
>Fiexs: commit 738136a0e375 ("netlink: split up copies in the
>ack construction")
>Signed-off-by: Tao Chen <chentao=2Ekernel@linux=2Ealibaba=2Ecom>
>---
> net/netlink/af_netlink=2Ec | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/net/netlink/af_netlink=2Ec b/net/netlink/af_netlink=2Ec
>index c6b8207e=2E=2E9d73dae 100644
>--- a/net/netlink/af_netlink=2Ec
>+++ b/net/netlink/af_netlink=2Ec
>@@ -2500,7 +2500,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlm=
sghdr *nlh, int err,
>=20
> 	skb =3D nlmsg_new(payload + tlvlen, GFP_KERNEL);
> 	if (!skb)
>-		goto err_bad_put;
>+		goto err_skb;
>=20
> 	rep =3D nlmsg_put(skb, NETLINK_CB(in_skb)=2Eportid, nlh->nlmsg_seq,
> 			NLMSG_ERROR, sizeof(*errmsg), flags);
>@@ -2528,6 +2528,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlm=
sghdr *nlh, int err,
> 	return;
>=20
> err_bad_put:
>+	kfree_skb(skb);
>+err_skb:
> 	NETLINK_CB(in_skb)=2Esk->sk_err =3D ENOBUFS;
> 	sk_error_report(NETLINK_CB(in_skb)=2Esk);
> }

It didn't do this before=2E=2E=2E Is this right?


--=20
Kees Cook