netdev - Re: [PATCH net] sctp: fail if no bound addresses can be used for a given scope

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: <CADvbK_coTyeDDyRHeUVPxWzx+bWXhMKZEXLr_YVwr08T=3u10Q@mail.gmail.com>
Date:   Mon, 23 Jan 2023 14:57:00 -0500
From:   Xin Long <lucien.xin@...il.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        Pietro Borrello <borrello@...g.uniroma1.it>
Subject: Re: [PATCH net] sctp: fail if no bound addresses can be used for a
 given scope

On Mon, Jan 23, 2023 at 1:00 PM Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
>
> Currently, if you bind the socket to something like:
>         servaddr.sin6_family = AF_INET6;
>         servaddr.sin6_port = htons(0);
>         servaddr.sin6_scope_id = 0;
>         inet_pton(AF_INET6, "::1", &servaddr.sin6_addr);
>
> And then request a connect to:
>         connaddr.sin6_family = AF_INET6;
>         connaddr.sin6_port = htons(20000);
>         connaddr.sin6_scope_id = if_nametoindex("lo");
>         inet_pton(AF_INET6, "fe88::1", &connaddr.sin6_addr);
>
> What the stack does is:
>  - bind the socket
>  - create a new asoc
>  - to handle the connect
>    - copy the addresses that can be used for the given scope
>    - try to connect
>
> But the copy returns 0 addresses, and the effect is that it ends up
> trying to connect as if the socket wasn't bound, which is not the
> desired behavior. This unexpected behavior also allows KASLR leaks
> through SCTP diag interface.
>
> The fix here then is, if when trying to copy the addresses that can
> be used for the scope used in connect() it returns 0 addresses, bail
> out. This is what TCP does with a similar reproducer.
>
> Reported-by: Pietro Borrello <borrello@...g.uniroma1.it>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> ---
>  net/sctp/bind_addr.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
> index 59e653b528b1faec6c6fcf73f0dd42633880e08d..6b95d3ba8fe1cecf4d75956bf87546b1f1a81c4f 100644
> --- a/net/sctp/bind_addr.c
> +++ b/net/sctp/bind_addr.c
> @@ -73,6 +73,12 @@ int sctp_bind_addr_copy(struct net *net, struct sctp_bind_addr *dest,
>                 }
>         }
>
> +       /* If somehow no addresses were found that can be used with this
> +        * scope, it's an error.
> +        */
> +       if (list_empty(&dest->address_list))
> +               error = -ENETUNREACH;
> +
>  out:
>         if (error)
>                 sctp_bind_addr_clean(dest);
> --
> 2.39.0
>
Reviewed-by: Xin Long <lucien.xin@...il.com>