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[2.205.64.187]) by smtp.gmail.com with ESMTPSA id y7-20020a1709060a8700b0098f99048053sm2097490ejf.148.2023.06.26.14.59.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jun 2023 14:59:59 -0700 (PDT) From: Alexander Mikhalitsyn To: davem@davemloft.net Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Alexander Mikhalitsyn , Luiz Augusto von Dentz , Eric Dumazet , Jakub Kicinski , Christian Brauner , Kuniyuki Iwashima , linux-bluetooth@vger.kernel.org Subject: [PATCH net-next] net: scm: introduce and use scm_recv_unix helper Date: Mon, 26 Jun 2023 23:59:51 +0200 Message-Id: <20230626215951.563715-1-aleksandr.mikhalitsyn@canonical.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org Recently, our friends from bluetooth subsystem reported [1] that after ("scm: add SO_PASSPIDFD and SCM_PIDFD") scm_recv helper become unusable in kernel modules (because it uses unexported pidfd_prepare() API). We were aware of this issue and workarounded it in a hard way by ("af_unix: Kconfig: make CONFIG_UNIX bool"). But recently a new functionality was added in the scope of 817efd3cad74 ("Bluetooth: hci_sock: Forward credentials to monitor") and after that bluetooth can't be compiled as a kernel module. After some discussion in [1] we decided to split scm_recv into two helpers, one won't support SCM_PIDFD (used for unix sockets), and another one will be completely the same as it was before ("scm: add SO_PASSPIDFD and SCM_PIDFD"). [1] https://lore.kernel.org/lkml/CAJqdLrpFcga4n7wxBhsFqPQiN8PKFVr6U10fKcJ9W7AcZn+o6Q@mail.gmail.com/ Cc: Luiz Augusto von Dentz Cc: "David S. Miller" Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Christian Brauner Cc: Kuniyuki Iwashima Cc: linux-kernel@vger.kernel.org Cc: linux-bluetooth@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: Alexander Mikhalitsyn --- include/net/scm.h | 35 +++++++++++++++++++++++++---------- net/unix/af_unix.c | 4 ++-- 2 files changed, 27 insertions(+), 12 deletions(-) diff --git a/include/net/scm.h b/include/net/scm.h index c67f765a165b..409b8efda2c9 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -151,8 +151,8 @@ static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm fd_install(pidfd, pidfd_file); } -static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, - struct scm_cookie *scm, int flags) +static inline bool __scm_recv_common(struct socket *sock, struct msghdr *msg, + struct scm_cookie *scm, int flags) { if (!msg->msg_control) { if (test_bit(SOCK_PASSCRED, &sock->flags) || @@ -160,7 +160,7 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, scm->fp || scm_has_secdata(sock)) msg->msg_flags |= MSG_CTRUNC; scm_destroy(scm); - return; + return false; } if (test_bit(SOCK_PASSCRED, &sock->flags)) { @@ -173,19 +173,34 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds); } - if (test_bit(SOCK_PASSPIDFD, &sock->flags)) - scm_pidfd_recv(msg, scm); + scm_passec(sock, msg, scm); - scm_destroy_cred(scm); + if (scm->fp) + scm_detach_fds(msg, scm); - scm_passec(sock, msg, scm); + return true; +} - if (!scm->fp) +static inline void scm_recv(struct socket *sock, struct msghdr *msg, + struct scm_cookie *scm, int flags) +{ + if (!__scm_recv_common(sock, msg, scm, flags)) return; - - scm_detach_fds(msg, scm); + + scm_destroy_cred(scm); } +static inline void scm_recv_unix(struct socket *sock, struct msghdr *msg, + struct scm_cookie *scm, int flags) +{ + if (!__scm_recv_common(sock, msg, scm, flags)) + return; + + if (test_bit(SOCK_PASSPIDFD, &sock->flags)) + scm_pidfd_recv(msg, scm); + + scm_destroy_cred(scm); +} #endif /* __LINUX_NET_SCM_H */ diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index f2f234f0b92c..20ac83e012e4 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2427,7 +2427,7 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size, } err = (flags & MSG_TRUNC) ? skb->len - skip : size; - scm_recv(sock, msg, &scm, flags); + scm_recv_unix(sock, msg, &scm, flags); out_free: skb_free_datagram(sk, skb); @@ -2808,7 +2808,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, mutex_unlock(&u->iolock); if (state->msg && check_creds) - scm_recv(sock, state->msg, &scm, flags); + scm_recv_unix(sock, state->msg, &scm, flags); else scm_destroy(&scm); out: