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[95.91.243.213]) by smtp.gmail.com with ESMTPSA id ci18-20020a170907267200b009659ecdf29fsm2753044ejc.1.2023.05.10.07.43.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 May 2023 07:43:23 -0700 (PDT) From: Alexander Mikhalitsyn To: nhorman@tuxdriver.com Cc: davem@davemloft.net, Alexander Mikhalitsyn , Daniel Borkmann , Christian Brauner , Stanislav Fomichev , Marcelo Ricardo Leitner , Xin Long , linux-sctp@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next v2] sctp: add bpf_bypass_getsockopt proto callback Date: Wed, 10 May 2023 16:42:58 +0200 Message-Id: <20230510144258.1343471-1-aleksandr.mikhalitsyn@canonical.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Add bpf_bypass_getsockopt proto callback and filter out SCTP_SOCKOPT_PEELOFF and SCTP_SOCKOPT_PEELOFF_FLAGS socket options from running eBPF hook on them. These 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 fdtab= le. This patch was born as a result of discussion around a new SCM_PIDFD interf= ace: https://lore.kernel.org/all/20230413133355.350571-3-aleksandr.mikhalitsyn@c= anonical.com/ Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks") Cc: Daniel Borkmann Cc: Christian Brauner Cc: Stanislav Fomichev Cc: Neil Horman Cc: Marcelo Ricardo Leitner Cc: Xin Long Cc: linux-sctp@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Suggested-by: Stanislav Fomichev Acked-by: Stanislav Fomichev Signed-off-by: Alexander Mikhalitsyn --- net/sctp/socket.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/net/sctp/socket.c b/net/sctp/socket.c index cda8c2874691..fed6057beb60 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -8281,6 +8281,29 @@ static int sctp_getsockopt(struct sock *sk, int leve= l, int optname, return retval; } =20 +static bool sctp_bpf_bypass_getsockopt(int level, int optname) +{ + /* + * These 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 = fdtable. + * + * Let's prevent bpf cgroup hook from running on them. + */ + if (level =3D=3D SOL_SCTP) { + switch (optname) { + case SCTP_SOCKOPT_PEELOFF: + case SCTP_SOCKOPT_PEELOFF_FLAGS: + return true; + default: + return false; + } + } + + return false; +} + static int sctp_hash(struct sock *sk) { /* STUB */ @@ -9650,6 +9673,7 @@ struct proto sctp_prot =3D { .shutdown =3D sctp_shutdown, .setsockopt =3D sctp_setsockopt, .getsockopt =3D sctp_getsockopt, + .bpf_bypass_getsockopt =3D sctp_bpf_bypass_getsockopt, .sendmsg =3D sctp_sendmsg, .recvmsg =3D sctp_recvmsg, .bind =3D sctp_bind, @@ -9705,6 +9729,7 @@ struct proto sctpv6_prot =3D { .shutdown =3D sctp_shutdown, .setsockopt =3D sctp_setsockopt, .getsockopt =3D sctp_getsockopt, + .bpf_bypass_getsockopt =3D sctp_bpf_bypass_getsockopt, .sendmsg =3D sctp_sendmsg, .recvmsg =3D sctp_recvmsg, .bind =3D sctp_bind, --=20 2.34.1