* [PATCH] net/unix: pass pidfd flags via SCM_PIDFD cmsg
@ 2024-11-13 21:02 Stas Sergeev
2024-11-14 2:50 ` Kuniyuki Iwashima
0 siblings, 1 reply; 3+ messages in thread
From: Stas Sergeev @ 2024-11-13 21:02 UTC (permalink / raw)
To: linux-kernel
Cc: Stas Sergeev, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Simon Horman, Shuah Khan, Christian Brauner,
Jens Axboe, Willem de Bruijn, Pavel Begunkov,
Gabriel Krisman Bertazi, Mina Almasry, Oleg Nesterov,
Tycho Andersen, Al Viro, Kuniyuki Iwashima, Gou Hao,
Abhishek Chauhan, Michal Luczaj, Kees Cook, netdev,
linux-kselftest
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.
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: 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 | 10 ++-
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, 106 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..bc64d516b226 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -8,6 +8,7 @@
#include <linux/file.h>
#include <linux/security.h>
#include <linux/pid.h>
+#include <linux/pidfs.h>
#include <linux/nsproxy.h>
#include <linux/sched/signal.h>
#include <net/compat.h>
@@ -48,6 +49,7 @@ 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);
@@ -137,6 +139,7 @@ static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm
{
struct file *pidfd_file = NULL;
int len, pidfd;
+ int err;
/* put_cmsg() doesn't return an error if CMSG is truncated,
* that's why we need to opencode these checks here.
@@ -154,7 +157,12 @@ 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);
+ err = pidfd_validate_flags(scm->pidfd_flags);
+ if (err) {
+ msg->msg_flags |= MSG_CTRUNC;
+ return;
+ }
+ 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);
--
2.47.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] net/unix: pass pidfd flags via SCM_PIDFD cmsg
2024-11-13 21:02 [PATCH] net/unix: pass pidfd flags via SCM_PIDFD cmsg Stas Sergeev
@ 2024-11-14 2:50 ` Kuniyuki Iwashima
2024-11-14 9:21 ` stsp
0 siblings, 1 reply; 3+ messages in thread
From: Kuniyuki Iwashima @ 2024-11-14 2:50 UTC (permalink / raw)
To: stsp2
Cc: almasrymina, asml.silence, axboe, brauner, davem, edumazet,
gouhao, horms, kees, krisman, kuba, kuniyu, linux-kernel,
linux-kselftest, mhal, netdev, oleg, pabeni, quic_abchauha, shuah,
tandersen, viro, willemb
From: Stas Sergeev <stsp2@yandex.ru>
Date: Thu, 14 Nov 2024 00:02:05 +0300
> @@ -154,7 +157,12 @@ 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);
> + err = pidfd_validate_flags(scm->pidfd_flags);
No neede to double check here, it's already checked in __scm_send().
> + if (err) {
> + msg->msg_flags |= MSG_CTRUNC;
> + return;
> + }
> + pidfd = pidfd_prepare(scm->pid, scm->pidfd_flags, &pidfd_file);
>
> if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) {
> if (pidfd_file) {
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] net/unix: pass pidfd flags via SCM_PIDFD cmsg
2024-11-14 2:50 ` Kuniyuki Iwashima
@ 2024-11-14 9:21 ` stsp
0 siblings, 0 replies; 3+ messages in thread
From: stsp @ 2024-11-14 9:21 UTC (permalink / raw)
To: Kuniyuki Iwashima
Cc: almasrymina, asml.silence, axboe, brauner, davem, edumazet,
gouhao, horms, kees, krisman, kuba, linux-kernel, linux-kselftest,
mhal, netdev, oleg, pabeni, quic_abchauha, shuah, tandersen, viro,
willemb
14.11.2024 05:50, Kuniyuki Iwashima пишет:
> From: Stas Sergeev <stsp2@yandex.ru>
> Date: Thu, 14 Nov 2024 00:02:05 +0300
>> @@ -154,7 +157,12 @@ 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);
>> + err = pidfd_validate_flags(scm->pidfd_flags);
> No neede to double check here, it's already checked in __scm_send().
Done and sent v2, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-11-13 21:02 [PATCH] net/unix: pass pidfd flags via SCM_PIDFD cmsg Stas Sergeev
2024-11-14 2:50 ` Kuniyuki Iwashima
2024-11-14 9:21 ` stsp
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