netdev - Re: [PATCH net-next] netlink: Fix potential skb memleak in netlink

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Date:   Wed, 02 Nov 2022 08:05:00 -0700
From:   Kees Cook <kees@...nel.org>
To:     Tao Chen <chentao.kernel@...ux.alibaba.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Johannes Berg <johannes@...solutions.net>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Petr Machata <petrm@...dia.com>,
        Kees Cook <keescook@...omium.org>,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
CC:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] netlink: Fix potential skb memleak in netlink_ack

On November 2, 2022 5:08:20 AM PDT, Tao Chen <chentao.kernel@...ux.alibaba.com> wrote:
>We should clean the skb resource if nlmsg_put/append failed
>, so fix it.
>
>Fiexs: commit 738136a0e375 ("netlink: split up copies in the
>ack construction")
>Signed-off-by: Tao Chen <chentao.kernel@...ux.alibaba.com>
>---
> net/netlink/af_netlink.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
>index c6b8207e..9d73dae 100644
>--- a/net/netlink/af_netlink.c
>+++ b/net/netlink/af_netlink.c
>@@ -2500,7 +2500,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
> 
> 	skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
> 	if (!skb)
>-		goto err_bad_put;
>+		goto err_skb;
> 
> 	rep = nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
> 			NLMSG_ERROR, sizeof(*errmsg), flags);
>@@ -2528,6 +2528,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
> 	return;
> 
> err_bad_put:
>+	kfree_skb(skb);
>+err_skb:
> 	NETLINK_CB(in_skb).sk->sk_err = ENOBUFS;
> 	sk_error_report(NETLINK_CB(in_skb).sk);
> }

It didn't do this before... Is this right?


-- 
Kees Cook