@@ -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 */
@@ -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;
@@ -62,6 +62,7 @@ struct unix_skb_parms {
#ifdef CONFIG_SECURITY_NETWORK
u32 secid; /* Security ID */
#endif
+ u32 pidfd_flags;
u32 consumed;
} __randomize_layout;
@@ -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) {
@@ -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;
@@ -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;
}
@@ -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;
@@ -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;
}
@@ -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(-)