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Miller" , Sasha Levin Subject: [PATCH 5.15 042/532] sctp: add bpf_bypass_getsockopt proto callback Date: Fri, 21 Jul 2023 17:59:06 +0200 Message-ID: <20230721160616.927524288@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230721160614.695323302@linuxfoundation.org> References: <20230721160614.695323302@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1772061564535051447 X-GMAIL-MSGID: 1772061564535051447 From: Alexander Mikhalitsyn [ Upstream commit 2598619e012cee5273a2821441b9a051ad931249 ] 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 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 Acked-by: Xin Long Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/sctp/socket.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 2bbc81ddb9e08..ed35d4a4c5253 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -8287,6 +8287,22 @@ 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 */ @@ -9655,6 +9671,7 @@ 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, @@ -9707,6 +9724,7 @@ 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,