netdev - Re: [PATCH v2 bpf 1/2] bpf, sockmap: fix potential msg memory leak

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAM_iQpXwTJ4kKNtcH27VVvX+bYFKTvVnM_RtP5G7zg_Nt9QBYw@mail.gmail.com>
Date:   Fri, 2 Jul 2021 12:54:01 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 bpf 1/2] bpf, sockmap: fix potential msg memory leak

On Thu, Jul 1, 2021 at 5:12 PM John Fastabend <john.fastabend@...il.com> wrote:
>
> If skb_linearize is needed and fails we could leak a msg on the error
> handling. To fix ensure we kfree the msg block before returning error.
> Found during code review.
>
> Fixes: 4363023d2668e ("bpf, sockmap: Avoid failures from skb_to_sgvec when skb has frag_list")
> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> ---
>  net/core/skmsg.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/skmsg.c b/net/core/skmsg.c
> index 9b6160a191f8..22603289c2b2 100644
> --- a/net/core/skmsg.c
> +++ b/net/core/skmsg.c
> @@ -505,8 +505,10 @@ static int sk_psock_skb_ingress_enqueue(struct sk_buff *skb,
>          * drop the skb. We need to linearize the skb so that the mapping
>          * in skb_to_sgvec can not error.
>          */
> -       if (skb_linearize(skb))
> +       if (skb_linearize(skb)) {
> +               kfree(msg);
>                 return -EAGAIN;
> +       }
>         num_sge = skb_to_sgvec(skb, msg->sg.data, 0, skb->len);
>         if (unlikely(num_sge < 0)) {
>                 kfree(msg);

I think it is better to let whoever allocates msg free it, IOW,
let sk_psock_skb_ingress_enqueue()'s callers handle its failure.

Thanks.