[PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

[PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

[Alexander Mikhalitsyn]

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@iogearbox.net>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: linux-sctp@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Suggested-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
---
v3: fix commit description and remove comments
v2: filter out SCTP_SOCKOPT_CONNECTX3
---
 net/sctp/socket.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index cda8c2874691..a68e1d541b12 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -8281,6 +8281,22 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname,
 	return retval;
 }
 
+static bool sctp_bpf_bypass_getsockopt(int level, int optname)
+{
+	if (level == SOL_SCTP) {
+		switch (optname) {
+		case SCTP_SOCKOPT_PEELOFF:
+		case SCTP_SOCKOPT_PEELOFF_FLAGS:
+		case SCTP_SOCKOPT_CONNECTX3:
+			return true;
+		default:
+			return false;
+		}
+	}
+
+	return false;
+}
+
 static int sctp_hash(struct sock *sk)
 {
 	/* STUB */
@@ -9650,6 +9666,7 @@ struct proto sctp_prot = {
 	.shutdown    =	sctp_shutdown,
 	.setsockopt  =	sctp_setsockopt,
 	.getsockopt  =	sctp_getsockopt,
+	.bpf_bypass_getsockopt	= sctp_bpf_bypass_getsockopt,
 	.sendmsg     =	sctp_sendmsg,
 	.recvmsg     =	sctp_recvmsg,
 	.bind        =	sctp_bind,
@@ -9705,6 +9722,7 @@ struct proto sctpv6_prot = {
 	.shutdown	= sctp_shutdown,
 	.setsockopt	= sctp_setsockopt,
 	.getsockopt	= sctp_getsockopt,
+	.bpf_bypass_getsockopt	= sctp_bpf_bypass_getsockopt,
 	.sendmsg	= sctp_sendmsg,
 	.recvmsg	= sctp_recvmsg,
 	.bind		= sctp_bind,
-- 
2.34.1

Re: [PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

[Marcelo Ricardo Leitner]

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@iogearbox.net>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: Stanislav Fomichev <sdf@google.com>
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> Cc: Xin Long <lucien.xin@gmail.com>
> Cc: linux-sctp@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Suggested-by: Stanislav Fomichev <sdf@google.com>
> Acked-by: Stanislav Fomichev <sdf@google.com>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>

Thx!

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Re: [PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

[Xin Long]

On Thu, May 11, 2023 at 9:33 AM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.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@iogearbox.net>
> > Cc: Christian Brauner <brauner@kernel.org>
> > Cc: Stanislav Fomichev <sdf@google.com>
> > Cc: Neil Horman <nhorman@tuxdriver.com>
> > Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> > Cc: Xin Long <lucien.xin@gmail.com>
> > Cc: linux-sctp@vger.kernel.org
> > Cc: linux-kernel@vger.kernel.org
> > Cc: netdev@vger.kernel.org
> > Suggested-by: Stanislav Fomichev <sdf@google.com>
> > Acked-by: Stanislav Fomichev <sdf@google.com>
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
>
> Thx!
>
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Xin Long <lucien.xin@gmail.com>

Re: [PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Thu, 11 May 2023 15:25:06 +0200 you 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.
> 
> [...]

Here is the summary with links:
  - [net-next,v3] sctp: add bpf_bypass_getsockopt proto callback
    https://git.kernel.org/netdev/net-next/c/2598619e012c

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback

[Christian Brauner]

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@iogearbox.net>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: Stanislav Fomichev <sdf@google.com>
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> Cc: Xin Long <lucien.xin@gmail.com>
> Cc: linux-sctp@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Suggested-by: Stanislav Fomichev <sdf@google.com>
> Acked-by: Stanislav Fomichev <sdf@google.com>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
> ---

Reviewed-by: Christian Brauner <brauner@kernel.org>