linux-kernel - Re: [PATCH net-next v3] sctp: add bpf_bypass

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Message-ID: <CADvbK_daDKfwDimJ=uovyO86i4KJZM32305fG70pSWw3Qe89Pg@mail.gmail.com>
Date:   Thu, 11 May 2023 10:20:57 -0400
From:   Xin Long <lucien.xin@...il.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>,
        nhorman@...driver.com, davem@...emloft.net,
        Daniel Borkmann <daniel@...earbox.net>,
        Christian Brauner <brauner@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        linux-sctp@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

On Thu, May 11, 2023 at 9:33 AM Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
>
> On Thu, May 11, 2023 at 03:25:06PM +0200, Alexander Mikhalitsyn wrote:
> > Implement ->bpf_bypass_getsockopt proto callback and filter out
> > SCTP_SOCKOPT_PEELOFF, SCTP_SOCKOPT_PEELOFF_FLAGS and SCTP_SOCKOPT_CONNECTX3
> > socket options from running eBPF hook on them.
> >
> > SCTP_SOCKOPT_PEELOFF and SCTP_SOCKOPT_PEELOFF_FLAGS options do fd_install(),
> > and if BPF_CGROUP_RUN_PROG_GETSOCKOPT hook returns an error after success of
> > the original handler sctp_getsockopt(...), userspace will receive an error
> > from getsockopt syscall and will be not aware that fd was successfully
> > installed into a fdtable.
> >
> > As pointed by Marcelo Ricardo Leitner it seems reasonable to skip
> > bpf getsockopt hook for SCTP_SOCKOPT_CONNECTX3 sockopt too.
> > Because internaly, it triggers connect() and if error is masked
> > then userspace will be confused.
> >
> > This patch was born as a result of discussion around a new SCM_PIDFD interface:
> > https://lore.kernel.org/all/20230413133355.350571-3-aleksandr.mikhalitsyn@canonical.com/
> >
> > Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
> > Cc: Daniel Borkmann <daniel@...earbox.net>
> > Cc: Christian Brauner <brauner@...nel.org>
> > Cc: Stanislav Fomichev <sdf@...gle.com>
> > Cc: Neil Horman <nhorman@...driver.com>
> > Cc: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> > Cc: Xin Long <lucien.xin@...il.com>
> > Cc: linux-sctp@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Cc: netdev@...r.kernel.org
> > Suggested-by: Stanislav Fomichev <sdf@...gle.com>
> > Acked-by: Stanislav Fomichev <sdf@...gle.com>
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
>
> Thx!
>
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Acked-by: Xin Long <lucien.xin@...il.com>