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[2.205.64.187]) by smtp.gmail.com with ESMTPSA id b16-20020a170906491000b0095342bfb701sm315592ejq.16.2023.06.08.13.26.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jun 2023 13:26:47 -0700 (PDT) From: Alexander Mikhalitsyn To: davem@davemloft.net Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Alexander Mikhalitsyn , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Leon Romanovsky , David Ahern , Arnd Bergmann , Kees Cook , Christian Brauner , Kuniyuki Iwashima , Lennart Poettering , Luca Boccassi , linux-arch@vger.kernel.org Subject: [PATCH net-next v7 1/4] scm: add SO_PASSPIDFD and SCM_PIDFD Date: Thu, 8 Jun 2023 22:26:25 +0200 Message-Id: <20230608202628.837772-2-aleksandr.mikhalitsyn@canonical.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230608202628.837772-1-aleksandr.mikhalitsyn@canonical.com> References: <20230608202628.837772-1-aleksandr.mikhalitsyn@canonical.com> 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" Implement SCM_PIDFD, a new type of CMSG type analogical to SCM_CREDENTIALS, but it contains pidfd instead of plain pid, which allows programmers not to care about PID reuse problem. We mask SO_PASSPIDFD feature if CONFIG_UNIX is not builtin because it depends on a pidfd_prepare() API which is not exported to the kernel modules. Idea comes from UAPI kernel group: https://uapi-group.org/kernel-features/ Big thanks to Christian Brauner and Lennart Poettering for productive discussions about this. Cc: "David S. Miller" Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Cc: Leon Romanovsky Cc: David Ahern Cc: Arnd Bergmann Cc: Kees Cook Cc: Christian Brauner Cc: Kuniyuki Iwashima Cc: Lennart Poettering Cc: Luca Boccassi Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Cc: linux-arch@vger.kernel.org Tested-by: Luca Boccassi Reviewed-by: Kuniyuki Iwashima Reviewed-by: Christian Brauner Signed-off-by: Alexander Mikhalitsyn Reviewed-by: Alexander Mikhalitsyn Reviewed-by: Eric Dumazet Tested-by: Heiko Carstens --- v7: - removed CONFIG_UNIX checks, because we've converted CONFIG_UNIX to be bo= olean v6: - disable feature when CONFIG_UNIX=3Dn/m (pidfd_prepare API is not exporte= d to modules) v5: - no changes v4: - fixed silent fd_install if writting of CMSG to the userspace fails (poin= ted by Christian) v2: According to review comments from Kuniyuki Iwashima and Christian Brauner: - use pidfd_create(..) retval as a result - whitespace change --- arch/alpha/include/uapi/asm/socket.h | 2 ++ arch/mips/include/uapi/asm/socket.h | 2 ++ arch/parisc/include/uapi/asm/socket.h | 2 ++ arch/sparc/include/uapi/asm/socket.h | 2 ++ include/linux/net.h | 1 + include/linux/socket.h | 1 + include/net/scm.h | 39 +++++++++++++++++++++++-- include/uapi/asm-generic/socket.h | 2 ++ net/core/sock.c | 11 +++++++ net/mptcp/sockopt.c | 1 + net/unix/af_unix.c | 18 ++++++++---- tools/include/uapi/asm-generic/socket.h | 2 ++ 12 files changed, 76 insertions(+), 7 deletions(-) diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi= /asm/socket.h index 739891b94136..ff310613ae64 100644 --- a/arch/alpha/include/uapi/asm/socket.h +++ b/arch/alpha/include/uapi/asm/socket.h @@ -137,6 +137,8 @@ =20 #define SO_RCVMARK 75 =20 +#define SO_PASSPIDFD 76 + #if !defined(__KERNEL__) =20 #if __BITS_PER_LONG =3D=3D 64 diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/a= sm/socket.h index 18f3d95ecfec..762dcb80e4ec 100644 --- a/arch/mips/include/uapi/asm/socket.h +++ b/arch/mips/include/uapi/asm/socket.h @@ -148,6 +148,8 @@ =20 #define SO_RCVMARK 75 =20 +#define SO_PASSPIDFD 76 + #if !defined(__KERNEL__) =20 #if __BITS_PER_LONG =3D=3D 64 diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/ua= pi/asm/socket.h index f486d3dfb6bb..df16a3e16d64 100644 --- a/arch/parisc/include/uapi/asm/socket.h +++ b/arch/parisc/include/uapi/asm/socket.h @@ -129,6 +129,8 @@ =20 #define SO_RCVMARK 0x4049 =20 +#define SO_PASSPIDFD 0x404A + #if !defined(__KERNEL__) =20 #if __BITS_PER_LONG =3D=3D 64 diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi= /asm/socket.h index 2fda57a3ea86..6e2847804fea 100644 --- a/arch/sparc/include/uapi/asm/socket.h +++ b/arch/sparc/include/uapi/asm/socket.h @@ -130,6 +130,8 @@ =20 #define SO_RCVMARK 0x0054 =20 +#define SO_PASSPIDFD 0x0055 + #if !defined(__KERNEL__) =20 =20 diff --git a/include/linux/net.h b/include/linux/net.h index b73ad8e3c212..c234dfbe7a30 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -43,6 +43,7 @@ struct net; #define SOCK_PASSSEC 4 #define SOCK_SUPPORT_ZC 5 #define SOCK_CUSTOM_SOCKOPT 6 +#define SOCK_PASSPIDFD 7 =20 #ifndef ARCH_HAS_SOCKET_TYPES /** diff --git a/include/linux/socket.h b/include/linux/socket.h index bd1cc3238851..3451a08f70d1 100644 --- a/include/linux/socket.h +++ b/include/linux/socket.h @@ -177,6 +177,7 @@ static inline size_t msg_data_left(struct msghdr *msg) #define SCM_RIGHTS 0x01 /* rw: access rights (array of int) */ #define SCM_CREDENTIALS 0x02 /* rw: struct ucred */ #define SCM_SECURITY 0x03 /* rw: security label */ +#define SCM_PIDFD 0x04 /* ro: pidfd (int) */ =20 struct ucred { __u32 pid; diff --git a/include/net/scm.h b/include/net/scm.h index 585adc1346bd..c67f765a165b 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -120,12 +120,44 @@ static inline bool scm_has_secdata(struct socket *soc= k) } #endif /* CONFIG_SECURITY_NETWORK */ =20 +static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cooki= e *scm) +{ + struct file *pidfd_file =3D NULL; + int pidfd; + + /* + * put_cmsg() doesn't return an error if CMSG is truncated, + * that's why we need to opencode these checks here. + */ + if ((msg->msg_controllen <=3D sizeof(struct cmsghdr)) || + (msg->msg_controllen - sizeof(struct cmsghdr)) < sizeof(int)) { + msg->msg_flags |=3D MSG_CTRUNC; + return; + } + + WARN_ON_ONCE(!scm->pid); + pidfd =3D pidfd_prepare(scm->pid, 0, &pidfd_file); + + if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) { + if (pidfd_file) { + put_unused_fd(pidfd); + fput(pidfd_file); + } + + return; + } + + if (pidfd_file) + fd_install(pidfd, pidfd_file); +} + static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm, int flags) { if (!msg->msg_control) { - if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp || - scm_has_secdata(sock)) + if (test_bit(SOCK_PASSCRED, &sock->flags) || + test_bit(SOCK_PASSPIDFD, &sock->flags) || + scm->fp || scm_has_secdata(sock)) msg->msg_flags |=3D MSG_CTRUNC; scm_destroy(scm); return; @@ -141,6 +173,9 @@ static __inline__ void scm_recv(struct socket *sock, st= ruct msghdr *msg, put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds); } =20 + if (test_bit(SOCK_PASSPIDFD, &sock->flags)) + scm_pidfd_recv(msg, scm); + scm_destroy_cred(scm); =20 scm_passec(sock, msg, scm); diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/s= ocket.h index 638230899e98..b76169fdb80b 100644 --- a/include/uapi/asm-generic/socket.h +++ b/include/uapi/asm-generic/socket.h @@ -132,6 +132,8 @@ =20 #define SO_RCVMARK 75 =20 +#define SO_PASSPIDFD 76 + #if !defined(__KERNEL__) =20 #if __BITS_PER_LONG =3D=3D 64 || (defined(__x86_64__) && defined(__ILP32__= )) diff --git a/net/core/sock.c b/net/core/sock.c index 24f2761bdb1d..ed4eb4ba738b 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1246,6 +1246,13 @@ int sk_setsockopt(struct sock *sk, int level, int op= tname, clear_bit(SOCK_PASSCRED, &sock->flags); break; =20 + case SO_PASSPIDFD: + if (valbool) + set_bit(SOCK_PASSPIDFD, &sock->flags); + else + clear_bit(SOCK_PASSPIDFD, &sock->flags); + break; + case SO_TIMESTAMP_OLD: case SO_TIMESTAMP_NEW: case SO_TIMESTAMPNS_OLD: @@ -1732,6 +1739,10 @@ int sk_getsockopt(struct sock *sk, int level, int op= tname, v.val =3D !!test_bit(SOCK_PASSCRED, &sock->flags); break; =20 + case SO_PASSPIDFD: + v.val =3D !!test_bit(SOCK_PASSPIDFD, &sock->flags); + break; + case SO_PEERCRED: { struct ucred peercred; diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index d4258869ac48..e172a5848b0d 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -355,6 +355,7 @@ static int mptcp_setsockopt_sol_socket(struct mptcp_soc= k *msk, int optname, case SO_BROADCAST: case SO_BSDCOMPAT: case SO_PASSCRED: + case SO_PASSPIDFD: case SO_PASSSEC: case SO_RXQ_OVFL: case SO_WIFI_STATUS: diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 653136d68b32..c46c2f5d860c 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1361,7 +1361,8 @@ static int unix_dgram_connect(struct socket *sock, st= ruct sockaddr *addr, if (err) goto out; =20 - if (test_bit(SOCK_PASSCRED, &sock->flags) && + if ((test_bit(SOCK_PASSCRED, &sock->flags) || + test_bit(SOCK_PASSPIDFD, &sock->flags)) && !unix_sk(sk)->addr) { err =3D unix_autobind(sk); if (err) @@ -1469,7 +1470,8 @@ static int unix_stream_connect(struct socket *sock, s= truct sockaddr *uaddr, if (err) goto out; =20 - if (test_bit(SOCK_PASSCRED, &sock->flags) && !u->addr) { + if ((test_bit(SOCK_PASSCRED, &sock->flags) || + test_bit(SOCK_PASSPIDFD, &sock->flags)) && !u->addr) { err =3D unix_autobind(sk); if (err) goto out; @@ -1670,6 +1672,8 @@ static void unix_sock_inherit_flags(const struct sock= et *old, { if (test_bit(SOCK_PASSCRED, &old->flags)) set_bit(SOCK_PASSCRED, &new->flags); + if (test_bit(SOCK_PASSPIDFD, &old->flags)) + set_bit(SOCK_PASSPIDFD, &new->flags); if (test_bit(SOCK_PASSSEC, &old->flags)) set_bit(SOCK_PASSSEC, &new->flags); } @@ -1819,8 +1823,10 @@ static bool unix_passcred_enabled(const struct socke= t *sock, const struct sock *other) { return test_bit(SOCK_PASSCRED, &sock->flags) || + test_bit(SOCK_PASSPIDFD, &sock->flags) || !other->sk_socket || - test_bit(SOCK_PASSCRED, &other->sk_socket->flags); + test_bit(SOCK_PASSCRED, &other->sk_socket->flags) || + test_bit(SOCK_PASSPIDFD, &other->sk_socket->flags); } =20 /* @@ -1904,7 +1910,8 @@ static int unix_dgram_sendmsg(struct socket *sock, st= ruct msghdr *msg, goto out; } =20 - if (test_bit(SOCK_PASSCRED, &sock->flags) && !u->addr) { + if ((test_bit(SOCK_PASSCRED, &sock->flags) || + test_bit(SOCK_PASSPIDFD, &sock->flags)) && !u->addr) { err =3D unix_autobind(sk); if (err) goto out; @@ -2718,7 +2725,8 @@ static int unix_stream_read_generic(struct unix_strea= m_read_state *state, /* Never glue messages from different writers */ if (!unix_skb_scm_eq(skb, &scm)) break; - } else if (test_bit(SOCK_PASSCRED, &sock->flags)) { + } else if (test_bit(SOCK_PASSCRED, &sock->flags) || + test_bit(SOCK_PASSPIDFD, &sock->flags)) { /* Copy credentials */ scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid); unix_set_secdata(&scm, skb); diff --git a/tools/include/uapi/asm-generic/socket.h b/tools/include/uapi/a= sm-generic/socket.h index 8756df13be50..fbbc4bf53ee3 100644 --- a/tools/include/uapi/asm-generic/socket.h +++ b/tools/include/uapi/asm-generic/socket.h @@ -121,6 +121,8 @@ =20 #define SO_RCVMARK 75 =20 +#define SO_PASSPIDFD 76 + #if !defined(__KERNEL__) =20 #if __BITS_PER_LONG =3D=3D 64 || (defined(__x86_64__) && defined(__ILP32__= )) --=20 2.34.1