From a9c49cc2f5b578c4ffa0ee135aa552d06dec0e82 Mon Sep 17 00:00:00 2001 From: Alexander Mikhalitsyn Date: Tue, 27 Jun 2023 10:43:14 -0700 Subject: net: scm: introduce and use scm_recv_unix helper Recently, our friends from bluetooth subsystem reported [1] that after commit 5e2ff6704a27 ("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 commit 97154bcf4d1b ("af_unix: Kconfig: make CONFIG_UNIX bool"). But recently a new functionality was added in the scope of commit 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 commit 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD"). Link: https://lore.kernel.org/lkml/CAJqdLrpFcga4n7wxBhsFqPQiN8PKFVr6U10fKcJ9W7AcZn+o6Q@mail.gmail.com/ [1] Fixes: 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD") Signed-off-by: Alexander Mikhalitsyn Reviewed-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230627174314.67688-3-kuniyu@amazon.com Signed-off-by: Jakub Kicinski --- include/net/scm.h | 35 +++++++++++++++++++++++++---------- 1 file changed, 25 insertions(+), 10 deletions(-) (limited to 'include') diff --git a/include/net/scm.h b/include/net/scm.h index d456fc41b8bf..c5bcdf65f55c 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -153,8 +153,8 @@ 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) || @@ -162,7 +162,7 @@ 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)) { @@ -175,19 +175,34 @@ 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 */ -- cgit v1.2.3