| Message ID | 20241114091909.3552288-1-stsp2@yandex.ru (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] net/unix: pass pidfd flags via SCM_PIDFD cmsg | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch, async |
> [PATCH v2] net/unix: pass pidfd flags via SCM_PIDFD cmsg Please specify the target tree; net for fixes, net-next for others. https://www.kernel.org/doc/html/v6.11/process/maintainer-netdev.html [PATCH net-next v3] af_unix: pass ... From: Stas Sergeev <stsp2@yandex.ru> Date: Thu, 14 Nov 2024 12:19:09 +0300 > Currently SCM_PIDFD cmsg cannot be sent via unix socket > (returns -EINVAL) and SO_PASSPIDFD doesn't support flags. > The created pidfd always has flags set to 0. > > This patch implements SCM_PIDFD cmsg in AF_UNIX socket, which > can be used to send flags to SO_PASSPIDFD-enabled recipient. > > Self-test is added for the propagation of PIDFD_NONBLOCK flag. > > This is mainly needed for the future extensions, like eg this one: > https://lore.kernel.org/lkml/8288a08e-448b-43c2-82dc-59f87d0d9072@yandex.ru/T/#me1237e46deba8574b77834b7704e63559ffef9cb > where it was suggested to try solving the supplementary groups > problem with pidfd. > > Changes in v2: remove flags validation in scm_pidfd_recv(), as > suggested by Kuniyuki Iwashima <kuniyu@amazon.com> You can put this changelog and the following CC: under '---' so that they will disappear during merge. > > Signed-off-by: Stas Sergeev <stsp2@yandex.ru> > > CC: "David S. Miller" <davem@davemloft.net> > CC: Eric Dumazet <edumazet@google.com> > CC: Jakub Kicinski <kuba@kernel.org> > CC: Paolo Abeni <pabeni@redhat.com> > CC: Simon Horman <horms@kernel.org> > CC: Shuah Khan <shuah@kernel.org> > CC: Christian Brauner <brauner@kernel.org> > CC: Jens Axboe <axboe@kernel.dk> > CC: Willem de Bruijn <willemb@google.com> > CC: Pavel Begunkov <asml.silence@gmail.com> > CC: Gabriel Krisman Bertazi <krisman@suse.de> > CC: Mina Almasry <almasrymina@google.com> > CC: Oleg Nesterov <oleg@redhat.com> > CC: Tycho Andersen <tandersen@netflix.com> > CC: Al Viro <viro@zeniv.linux.org.uk> > CC: Kuniyuki Iwashima <kuniyu@amazon.com> > CC: Gou Hao <gouhao@uniontech.com> > CC: Abhishek Chauhan <quic_abchauha@quicinc.com> > CC: Michal Luczaj <mhal@rbox.co> > CC: Kees Cook <kees@kernel.org> > CC: Aleksa Sarai <cyphar@cyphar.com> > CC: linux-kernel@vger.kernel.org > CC: netdev@vger.kernel.org > CC: linux-kselftest@vger.kernel.org > --- ^^^ Here > include/linux/pidfs.h | 9 +++ > include/linux/socket.h | 2 +- > include/net/af_unix.h | 1 + > include/net/scm.h | 3 +- > kernel/pid.c | 6 +- > net/core/scm.c | 14 ++++ > net/core/sock.c | 1 + > net/unix/af_unix.c | 3 + > .../testing/selftests/net/af_unix/scm_pidfd.c | 70 +++++++++++++++++-- > 9 files changed, 99 insertions(+), 10 deletions(-) > > diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h > index 75bdf9807802..c4c5c1a0c2ad 100644 > --- a/include/linux/pidfs.h > +++ b/include/linux/pidfs.h > @@ -2,7 +2,16 @@ > #ifndef _LINUX_PID_FS_H > #define _LINUX_PID_FS_H > > +#include <uapi/linux/pidfd.h> > + > struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags); > void __init pidfs_init(void); > > +static inline int pidfd_validate_flags(unsigned int flags) > +{ > + if (flags & ~(PIDFD_NONBLOCK | PIDFD_THREAD)) > + return -EINVAL; > + return 0; > +} > + > #endif /* _LINUX_PID_FS_H */ > diff --git a/include/linux/socket.h b/include/linux/socket.h > index d18cc47e89bd..ee27d391e5aa 100644 > --- a/include/linux/socket.h > +++ b/include/linux/socket.h > @@ -178,7 +178,7 @@ 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) */ > +#define SCM_PIDFD 0x04 /* r: pidfd, w: pidfd_flags (int) */ > > struct ucred { > __u32 pid; > diff --git a/include/net/af_unix.h b/include/net/af_unix.h > index 63129c79b8cb..4bc197548c2f 100644 > --- a/include/net/af_unix.h > +++ b/include/net/af_unix.h > @@ -62,6 +62,7 @@ struct unix_skb_parms { > #ifdef CONFIG_SECURITY_NETWORK > u32 secid; /* Security ID */ > #endif > + u32 pidfd_flags; > u32 consumed; > } __randomize_layout; > > diff --git a/include/net/scm.h b/include/net/scm.h > index 0d35c7c77a74..1326edcacacb 100644 > --- a/include/net/scm.h > +++ b/include/net/scm.h > @@ -48,6 +48,7 @@ struct scm_cookie { > #ifdef CONFIG_SECURITY_NETWORK > u32 secid; /* Passed security ID */ > #endif > + u32 pidfd_flags; Now we consume 40 byes of cb[48]. If we need more storage in the future, we may want to save converted flags in __scm_send() and restore that in scm_pidfd_recv(). No need to do so now, just a note. > }; > > void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm); > @@ -154,7 +155,7 @@ static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm > if (!scm->pid) > return; > > - pidfd = pidfd_prepare(scm->pid, 0, &pidfd_file); > + pidfd = pidfd_prepare(scm->pid, scm->pidfd_flags, &pidfd_file); > > if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) { > if (pidfd_file) { > diff --git a/kernel/pid.c b/kernel/pid.c > index 2715afb77eab..b1100ae8ea63 100644 > --- a/kernel/pid.c > +++ b/kernel/pid.c > @@ -629,10 +629,12 @@ static int pidfd_create(struct pid *pid, unsigned int flags) > SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags) > { > int fd; > + int err; > struct pid *p; > > - if (flags & ~(PIDFD_NONBLOCK | PIDFD_THREAD)) > - return -EINVAL; > + err = pidfd_validate_flags(flags); > + if (err) > + return err; > > if (pid <= 0) > return -EINVAL; > diff --git a/net/core/scm.c b/net/core/scm.c > index 4f6a14babe5a..3bcdecdacd7e 100644 > --- a/net/core/scm.c > +++ b/net/core/scm.c > @@ -23,6 +23,7 @@ > #include <linux/security.h> > #include <linux/pid_namespace.h> > #include <linux/pid.h> > +#include <linux/pidfs.h> > #include <linux/nsproxy.h> > #include <linux/slab.h> > #include <linux/errqueue.h> > @@ -210,6 +211,19 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) > p->creds.gid = gid; > break; > } > + case SCM_PIDFD: > + { > + unsigned int flags; > + > + if (cmsg->cmsg_len != CMSG_LEN(sizeof(flags))) > + goto error; > + memcpy(&flags, CMSG_DATA(cmsg), sizeof(flags)); > + err = pidfd_validate_flags(flags); > + if (err) > + goto error; > + p->pidfd_flags = flags; > + break; > + } Now this allows sending pidfd without SO_PASSPIDFD, so you need to add a validation for "if (!msg->msg_control)" in __scm_recv_common(). > default: > goto error; > } > diff --git a/net/core/sock.c b/net/core/sock.c > index 039be95c40cf..d1fce437c035 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -2930,6 +2930,7 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg, > /* SCM_RIGHTS and SCM_CREDENTIALS are semantically in SOL_UNIX. */ > case SCM_RIGHTS: > case SCM_CREDENTIALS: > + case SCM_PIDFD: > break; > default: > return -EINVAL; > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > index 001ccc55ef0f..8b19dfec0221 100644 > --- a/net/unix/af_unix.c > +++ b/net/unix/af_unix.c > @@ -1892,6 +1892,7 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen > UNIXCB(skb).uid = scm->creds.uid; > UNIXCB(skb).gid = scm->creds.gid; > UNIXCB(skb).fp = NULL; > + UNIXCB(skb).pidfd_flags = scm->pidfd_flags; > unix_get_secdata(scm, skb); > if (scm->fp && send_fds) > err = unix_attach_fds(scm, skb); > @@ -2486,6 +2487,7 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size, > memset(&scm, 0, sizeof(scm)); > > scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid); > + scm.pidfd_flags = UNIXCB(skb).pidfd_flags; > unix_set_secdata(&scm, skb); > > if (!(flags & MSG_PEEK)) { > @@ -2873,6 +2875,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, > test_bit(SOCK_PASSPIDFD, &sock->flags)) { > /* Copy credentials */ > scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid); > + scm.pidfd_flags = UNIXCB(skb).pidfd_flags; > unix_set_secdata(&scm, skb); > check_creds = true; > }
16.11.2024 04:10, Kuniyuki Iwashima пишет: >> [PATCH v2] net/unix: pass pidfd flags via SCM_PIDFD cmsg > Please specify the target tree; net for fixes, net-next for others. > https://www.kernel.org/doc/html/v6.11/process/maintainer-netdev.html > > [PATCH net-next v3] af_unix: pass ... Thanks for the link and the hints! All done.
16.11.2024 04:10, Kuniyuki Iwashima пишет: > Now this allows sending pidfd without SO_PASSPIDFD, so you need to > add a validation for "if (!msg->msg_control)" in __scm_recv_common(). Will do, thanks. Btw don't we need MSG_CTRUNC in such case even if "msg_control"exists? Or the established practice is to just drop cmsg silently? I mean, something like the below: --- a/include/net/scm.h +++ b/include/net/scm.h @@ -176,12 +176,19 @@ static inline bool __scm_recv_common(struct socket *sock, struct msghdr *msg, if (!msg->msg_control) { if (test_bit(SOCK_PASSCRED, &sock->flags) || test_bit(SOCK_PASSPIDFD, &sock->flags) || - scm->fp || scm_has_secdata(sock)) + scm->fp || scm_has_secdata(sock) || + scm->pidfd_flags) msg->msg_flags |= MSG_CTRUNC; scm_destroy(scm); return false; } + if (!test_bit(SOCK_PASSPIDFD, &sock->flags) && scm->pidfd_flags) { + msg->msg_flags |= MSG_CTRUNC; + scm_destroy(scm); + return false; + } + if (test_bit(SOCK_PASSCRED, &sock->flags)) { struct user_namespace *current_ns = current_user_ns(); struct ucred ucreds = {
16.11.2024 04:10, Kuniyuki Iwashima пишет: > Now this allows sending pidfd without SO_PASSPIDFD, so you need to > add a validation for "if (!msg->msg_control)" in __scm_recv_common(). Will do, thanks. Btw don't we need MSG_CTRUNC in such case even if "msg_control"exists? Or the established practice is to just drop cmsg silently? I mean, something like the below: --- a/include/net/scm.h +++ b/include/net/scm.h @@ -176,12 +176,19 @@ static inline bool __scm_recv_common(struct socket *sock, struct msghdr *msg, if (!msg->msg_control) { if (test_bit(SOCK_PASSCRED, &sock->flags) || test_bit(SOCK_PASSPIDFD, &sock->flags) || - scm->fp || scm_has_secdata(sock)) + scm->fp || scm_has_secdata(sock) || + scm->pidfd_flags) msg->msg_flags |= MSG_CTRUNC; scm_destroy(scm); return false; } + if (!test_bit(SOCK_PASSPIDFD, &sock->flags) && scm->pidfd_flags) { + msg->msg_flags |= MSG_CTRUNC; + scm_destroy(scm); + return false; + } + if (test_bit(SOCK_PASSCRED, &sock->flags)) { struct user_namespace *current_ns = current_user_ns(); struct ucred ucreds = {
diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h index 75bdf9807802..c4c5c1a0c2ad 100644 --- a/include/linux/pidfs.h +++ b/include/linux/pidfs.h @@ -2,7 +2,16 @@ #ifndef _LINUX_PID_FS_H #define _LINUX_PID_FS_H +#include <uapi/linux/pidfd.h> + struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags); void __init pidfs_init(void); +static inline int pidfd_validate_flags(unsigned int flags) +{ + if (flags & ~(PIDFD_NONBLOCK | PIDFD_THREAD)) + return -EINVAL; + return 0; +} + #endif /* _LINUX_PID_FS_H */ diff --git a/include/linux/socket.h b/include/linux/socket.h index d18cc47e89bd..ee27d391e5aa 100644 --- a/include/linux/socket.h +++ b/include/linux/socket.h @@ -178,7 +178,7 @@ 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) */ +#define SCM_PIDFD 0x04 /* r: pidfd, w: pidfd_flags (int) */ struct ucred { __u32 pid; diff --git a/include/net/af_unix.h b/include/net/af_unix.h index 63129c79b8cb..4bc197548c2f 100644 --- a/include/net/af_unix.h +++ b/include/net/af_unix.h @@ -62,6 +62,7 @@ struct unix_skb_parms { #ifdef CONFIG_SECURITY_NETWORK u32 secid; /* Security ID */ #endif + u32 pidfd_flags; u32 consumed; } __randomize_layout; diff --git a/include/net/scm.h b/include/net/scm.h index 0d35c7c77a74..1326edcacacb 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -48,6 +48,7 @@ struct scm_cookie { #ifdef CONFIG_SECURITY_NETWORK u32 secid; /* Passed security ID */ #endif + u32 pidfd_flags; }; void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm); @@ -154,7 +155,7 @@ static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm if (!scm->pid) return; - pidfd = pidfd_prepare(scm->pid, 0, &pidfd_file); + pidfd = pidfd_prepare(scm->pid, scm->pidfd_flags, &pidfd_file); if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) { if (pidfd_file) { diff --git a/kernel/pid.c b/kernel/pid.c index 2715afb77eab..b1100ae8ea63 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -629,10 +629,12 @@ static int pidfd_create(struct pid *pid, unsigned int flags) SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags) { int fd; + int err; struct pid *p; - if (flags & ~(PIDFD_NONBLOCK | PIDFD_THREAD)) - return -EINVAL; + err = pidfd_validate_flags(flags); + if (err) + return err; if (pid <= 0) return -EINVAL; diff --git a/net/core/scm.c b/net/core/scm.c index 4f6a14babe5a..3bcdecdacd7e 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -23,6 +23,7 @@ #include <linux/security.h> #include <linux/pid_namespace.h> #include <linux/pid.h> +#include <linux/pidfs.h> #include <linux/nsproxy.h> #include <linux/slab.h> #include <linux/errqueue.h> @@ -210,6 +211,19 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) p->creds.gid = gid; break; } + case SCM_PIDFD: + { + unsigned int flags; + + if (cmsg->cmsg_len != CMSG_LEN(sizeof(flags))) + goto error; + memcpy(&flags, CMSG_DATA(cmsg), sizeof(flags)); + err = pidfd_validate_flags(flags); + if (err) + goto error; + p->pidfd_flags = flags; + break; + } default: goto error; } diff --git a/net/core/sock.c b/net/core/sock.c index 039be95c40cf..d1fce437c035 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2930,6 +2930,7 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg, /* SCM_RIGHTS and SCM_CREDENTIALS are semantically in SOL_UNIX. */ case SCM_RIGHTS: case SCM_CREDENTIALS: + case SCM_PIDFD: break; default: return -EINVAL; diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 001ccc55ef0f..8b19dfec0221 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1892,6 +1892,7 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen UNIXCB(skb).uid = scm->creds.uid; UNIXCB(skb).gid = scm->creds.gid; UNIXCB(skb).fp = NULL; + UNIXCB(skb).pidfd_flags = scm->pidfd_flags; unix_get_secdata(scm, skb); if (scm->fp && send_fds) err = unix_attach_fds(scm, skb); @@ -2486,6 +2487,7 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size, memset(&scm, 0, sizeof(scm)); scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid); + scm.pidfd_flags = UNIXCB(skb).pidfd_flags; unix_set_secdata(&scm, skb); if (!(flags & MSG_PEEK)) { @@ -2873,6 +2875,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, test_bit(SOCK_PASSPIDFD, &sock->flags)) { /* Copy credentials */ scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid); + scm.pidfd_flags = UNIXCB(skb).pidfd_flags; unix_set_secdata(&scm, skb); check_creds = true; } diff --git a/tools/testing/selftests/net/af_unix/scm_pidfd.c b/tools/testing/selftests/net/af_unix/scm_pidfd.c index 7e534594167e..1e70ff253a1d 100644 --- a/tools/testing/selftests/net/af_unix/scm_pidfd.c +++ b/tools/testing/selftests/net/af_unix/scm_pidfd.c @@ -5,6 +5,7 @@ #include <stddef.h> #include <stdio.h> #include <stdlib.h> +#include <fcntl.h> #include <sys/socket.h> #include <linux/socket.h> #include <unistd.h> @@ -15,6 +16,11 @@ #include <sys/types.h> #include <sys/wait.h> +/* There are problems including linux/pidfd.h, so define. */ +#ifndef PIDFD_NONBLOCK +#define PIDFD_NONBLOCK O_NONBLOCK +#endif + #include "../../kselftest_harness.h" #define clean_errno() (errno == 0 ? "None" : strerror(errno)) @@ -126,7 +132,7 @@ static pid_t get_pid_from_fdinfo_file(int pidfd, const char *key, size_t keylen) return result; } -static int cmsg_check(int fd) +static int cmsg_check(int fd, unsigned int pidfd_flags) { struct msghdr msg = { 0 }; struct cmsghdr *cmsg; @@ -136,6 +142,7 @@ static int cmsg_check(int fd) char control[CMSG_SPACE(sizeof(struct ucred)) + CMSG_SPACE(sizeof(int))] = { 0 }; int *pidfd = NULL; + unsigned int flags; pid_t parent_pid; int err; @@ -197,6 +204,13 @@ static int cmsg_check(int fd) return 1; } + flags = fcntl(*pidfd, F_GETFL, 0); + flags &= ~O_ACCMODE; + if (flags != pidfd_flags) { + log_err("SCM_PIDFD flags mismatch: %x != %x", flags, pidfd_flags); + return 1; + } + /* pidfd from SCM_PIDFD should point to the parent process PID */ parent_pid = get_pid_from_fdinfo_file(*pidfd, "Pid:", sizeof("Pid:") - 1); @@ -227,30 +241,49 @@ FIXTURE_VARIANT(scm_pidfd) { int type; bool abstract; + unsigned int flags; }; FIXTURE_VARIANT_ADD(scm_pidfd, stream_pathname) { .type = SOCK_STREAM, .abstract = 0, + .flags = 0, }; FIXTURE_VARIANT_ADD(scm_pidfd, stream_abstract) { .type = SOCK_STREAM, .abstract = 1, + .flags = 0, }; FIXTURE_VARIANT_ADD(scm_pidfd, dgram_pathname) { .type = SOCK_DGRAM, .abstract = 0, + .flags = 0, }; FIXTURE_VARIANT_ADD(scm_pidfd, dgram_abstract) { .type = SOCK_DGRAM, .abstract = 1, + .flags = 0, +}; + +FIXTURE_VARIANT_ADD(scm_pidfd, stream_nonblock) +{ + .type = SOCK_STREAM, + .abstract = 0, + .flags = PIDFD_NONBLOCK, +}; + +FIXTURE_VARIANT_ADD(scm_pidfd, dgram_nonblock) +{ + .type = SOCK_DGRAM, + .abstract = 0, + .flags = PIDFD_NONBLOCK, }; FIXTURE_SETUP(scm_pidfd) @@ -335,7 +368,7 @@ static void client(FIXTURE_DATA(scm_pidfd) *self, close(self->startup_pipe[1]); - if (cmsg_check(cfd)) { + if (cmsg_check(cfd, variant->flags)) { log_err("cmsg_check failed"); child_die(); } @@ -375,6 +408,27 @@ TEST_F(scm_pidfd, test) int err; int pfd; int child_status = 0; + char iobuf; + unsigned int pidfd_flags; + struct msghdr msg = { 0 }; + struct cmsghdr *cmsg; + struct iovec io = { + .iov_base = &iobuf, + .iov_len = sizeof(iobuf) + }; + union { + char buf[CMSG_SPACE(sizeof(pidfd_flags))]; + struct cmsghdr align; + } u; + + msg.msg_iov = &io; + msg.msg_iovlen = 1; + msg.msg_control = u.buf; + msg.msg_controllen = sizeof(u.buf); + cmsg = CMSG_FIRSTHDR(&msg); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_PIDFD; + cmsg->cmsg_len = CMSG_LEN(sizeof(pidfd_flags)); self->server = socket(AF_UNIX, variant->type, 0); ASSERT_NE(-1, self->server); @@ -414,12 +468,16 @@ TEST_F(scm_pidfd, test) close(self->startup_pipe[0]); if (variant->type == SOCK_DGRAM) { - err = sendto(pfd, "x", sizeof(char), 0, (struct sockaddr *)&self->client_addr->listen_addr, self->client_addr->addrlen); - ASSERT_NE(-1, err); - } else { - err = send(pfd, "x", sizeof(char), 0); + err = connect(pfd, + (struct sockaddr *)&self->client_addr->listen_addr, + self->client_addr->addrlen); ASSERT_NE(-1, err); } + iobuf = 'x'; + pidfd_flags = variant->flags; + memcpy(CMSG_DATA(cmsg), &pidfd_flags, sizeof(pidfd_flags)); + err = sendmsg(pfd, &msg, 0); + ASSERT_NE(-1, err); close(pfd); waitpid(self->client_pid, &child_status, 0);
Currently SCM_PIDFD cmsg cannot be sent via unix socket (returns -EINVAL) and SO_PASSPIDFD doesn't support flags. The created pidfd always has flags set to 0. This patch implements SCM_PIDFD cmsg in AF_UNIX socket, which can be used to send flags to SO_PASSPIDFD-enabled recipient. Self-test is added for the propagation of PIDFD_NONBLOCK flag. This is mainly needed for the future extensions, like eg this one: https://lore.kernel.org/lkml/8288a08e-448b-43c2-82dc-59f87d0d9072@yandex.ru/T/#me1237e46deba8574b77834b7704e63559ffef9cb where it was suggested to try solving the supplementary groups problem with pidfd. Changes in v2: remove flags validation in scm_pidfd_recv(), as suggested by Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: Stas Sergeev <stsp2@yandex.ru> CC: "David S. Miller" <davem@davemloft.net> CC: Eric Dumazet <edumazet@google.com> CC: Jakub Kicinski <kuba@kernel.org> CC: Paolo Abeni <pabeni@redhat.com> CC: Simon Horman <horms@kernel.org> CC: Shuah Khan <shuah@kernel.org> CC: Christian Brauner <brauner@kernel.org> CC: Jens Axboe <axboe@kernel.dk> CC: Willem de Bruijn <willemb@google.com> CC: Pavel Begunkov <asml.silence@gmail.com> CC: Gabriel Krisman Bertazi <krisman@suse.de> CC: Mina Almasry <almasrymina@google.com> CC: Oleg Nesterov <oleg@redhat.com> CC: Tycho Andersen <tandersen@netflix.com> CC: Al Viro <viro@zeniv.linux.org.uk> CC: Kuniyuki Iwashima <kuniyu@amazon.com> CC: Gou Hao <gouhao@uniontech.com> CC: Abhishek Chauhan <quic_abchauha@quicinc.com> CC: Michal Luczaj <mhal@rbox.co> CC: Kees Cook <kees@kernel.org> CC: Aleksa Sarai <cyphar@cyphar.com> CC: linux-kernel@vger.kernel.org CC: netdev@vger.kernel.org CC: linux-kselftest@vger.kernel.org --- include/linux/pidfs.h | 9 +++ include/linux/socket.h | 2 +- include/net/af_unix.h | 1 + include/net/scm.h | 3 +- kernel/pid.c | 6 +- net/core/scm.c | 14 ++++ net/core/sock.c | 1 + net/unix/af_unix.c | 3 + .../testing/selftests/net/af_unix/scm_pidfd.c | 70 +++++++++++++++++-- 9 files changed, 99 insertions(+), 10 deletions(-)