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Message-Id: <20230511132506.379102-1-aleksandr.mikhalitsyn@canonical.com> Date: Thu, 11 May 2023 15:25:06 +0200 From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com> To: nhorman@...driver.com Cc: davem@...emloft.net, Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>, Daniel Borkmann <daniel@...earbox.net>, Christian Brauner <brauner@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Marcelo Ricardo Leitner <marcelo.leitner@...il.com>, Xin Long <lucien.xin@...il.com>, linux-sctp@...r.kernel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org Subject: [PATCH net-next v3] sctp: add bpf_bypass_getsockopt proto callback 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> --- 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
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