From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: <maze@google.com>
Cc: <edumazet@google.com>, <eyal.birger@gmail.com>, <kuba@kernel.org>,
<larysa.zaremba@intel.com>, <netdev@vger.kernel.org>,
<pabeni@redhat.com>, <prohr@google.com>,
<simon.horman@corigine.com>, <zenczykowski@gmail.com>,
<kuniyu@amazon.com>
Subject: Re: [PATCH net v2] revert "net: align SO_RCVMARK required privileges with SO_MARK"
Date: Mon, 19 Jun 2023 17:17:57 -0700 [thread overview]
Message-ID: <20230620001757.13161-1-kuniyu@amazon.com> (raw)
In-Reply-To: <20230618103130.51628-1-maze@google.com>
From: Maciej Żenczykowski <maze@google.com>
Date: Sun, 18 Jun 2023 03:31:30 -0700
> This reverts commit 1f86123b9749 ("net: align SO_RCVMARK required
> privileges with SO_MARK") because the reasoning in the commit message
> is not really correct:
> SO_RCVMARK is used for 'reading' incoming skb mark (via cmsg), as such
> it is more equivalent to 'getsockopt(SO_MARK)' which has no priv check
> and retrieves the socket mark, rather than 'setsockopt(SO_MARK) which
> sets the socket mark and does require privs.
>
> Additionally incoming skb->mark may already be visible if
> sysctl_fwmark_reflect and/or sysctl_tcp_fwmark_accept are enabled.
>
> Furthermore, it is easier to block the getsockopt via bpf
> (either cgroup setsockopt hook, or via syscall filters)
> then to unblock it if it requires CAP_NET_RAW/ADMIN.
>
> On Android the socket mark is (among other things) used to store
> the network identifier a socket is bound to. Setting it is privileged,
> but retrieving it is not. We'd like unprivileged userspace to be able
> to read the network id of incoming packets (where mark is set via
> iptables [to be moved to bpf])...
>
> An alternative would be to add another sysctl to control whether
> setting SO_RCVMARK is privilged or not.
> (or even a MASK of which bits in the mark can be exposed)
> But this seems like over-engineering...
>
> Note: This is a non-trivial revert, due to later merged commit e42c7beee71d
> ("bpf: net: Consider has_current_bpf_ctx() when testing capable() in sk_setsockopt()")
> which changed both 'ns_capable' into 'sockopt_ns_capable' calls.
>
> Fixes: 1f86123b9749 ("net: align SO_RCVMARK required privileges with SO_MARK")
> Cc: Larysa Zaremba <larysa.zaremba@intel.com>
> Cc: Simon Horman <simon.horman@corigine.com>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Eyal Birger <eyal.birger@gmail.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Patrick Rohr <prohr@google.com>
> Signed-off-by: Maciej Żenczykowski <maze@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
> net/core/sock.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 24f2761bdb1d..6e5662ca00fe 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1362,12 +1362,6 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
> __sock_set_mark(sk, val);
> break;
> case SO_RCVMARK:
> - if (!sockopt_ns_capable(sock_net(sk)->user_ns, CAP_NET_RAW) &&
> - !sockopt_ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
> - ret = -EPERM;
> - break;
> - }
> -
> sock_valbool_flag(sk, SOCK_RCVMARK, valbool);
> break;
>
> --
> 2.41.0.162.gfafddb0af9-goog
next prev parent reply other threads:[~2023-06-20 0:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-05 8:12 [PATCH] net: revert "align SO_RCVMARK required privileges with SO_MARK" Maciej Żenczykowski
2023-06-05 15:27 ` Larysa Zaremba
2023-06-05 17:30 ` Simon Horman
2023-06-06 11:37 ` Paolo Abeni
2023-06-18 10:31 ` [PATCH net v2] revert "net: align " Maciej Żenczykowski
2023-06-19 14:12 ` Simon Horman
2023-06-20 0:17 ` Kuniyuki Iwashima [this message]
2023-06-22 10:00 ` patchwork-bot+netdevbpf
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