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scm: add SO_PASSPIDFD and SCM_PIDFD

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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" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: David Ahern <dsahern@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Tested-by: Luca Boccassi <bluca@debian.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Mikhalitsyn 2023-06-08 22:26:25 +02:00 committed by David S. Miller
parent 55d7c91406
commit 5e2ff6704a
12 changed files with 76 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
arch/alpha/include/uapi/asm/socket.h
View file

@ -137,6 +137,8 @@
#define SO_RCVMARK 75
#define SO_PASSPIDFD 76
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/mips/include/uapi/asm/socket.h
View file

@ -148,6 +148,8 @@
#define SO_RCVMARK 75
#define SO_PASSPIDFD 76
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/parisc/include/uapi/asm/socket.h
View file

@ -129,6 +129,8 @@
#define SO_RCVMARK 0x4049
#define SO_PASSPIDFD 0x404A
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/sparc/include/uapi/asm/socket.h
View file

@ -130,6 +130,8 @@
#define SO_RCVMARK 0x0054
#define SO_PASSPIDFD 0x0055
#if !defined(__KERNEL__)

1
include/linux/net.h
View file

@ -43,6 +43,7 @@ struct net;
#define SOCK_PASSSEC 4
#define SOCK_SUPPORT_ZC 5
#define SOCK_CUSTOM_SOCKOPT 6
#define SOCK_PASSPIDFD 7
#ifndef ARCH_HAS_SOCKET_TYPES
/**

1
include/linux/socket.h
View file

@ -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) */
struct ucred {
__u32 pid;

39
include/net/scm.h
View file

@ -120,12 +120,44 @@ static inline bool scm_has_secdata(struct socket *sock)
}
#endif /* CONFIG_SECURITY_NETWORK */
static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm)
{
struct file *pidfd_file = 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 <= sizeof(struct cmsghdr)) ||
(msg->msg_controllen - sizeof(struct cmsghdr)) < sizeof(int)) {
msg->msg_flags |= MSG_CTRUNC;
return;
}
WARN_ON_ONCE(!scm->pid);
pidfd = 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 |= MSG_CTRUNC;
scm_destroy(scm);
return;
@ -141,6 +173,9 @@ 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_destroy_cred(scm);
scm_passec(sock, msg, scm);

2
include/uapi/asm-generic/socket.h
View file

@ -132,6 +132,8 @@
#define SO_RCVMARK 75
#define SO_PASSPIDFD 76
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))

11
net/core/sock.c
View file

@ -1246,6 +1246,13 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
clear_bit(SOCK_PASSCRED, &sock->flags);
break;
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 optname,
v.val = !!test_bit(SOCK_PASSCRED, &sock->flags);
break;
case SO_PASSPIDFD:
v.val = !!test_bit(SOCK_PASSPIDFD, &sock->flags);
break;
case SO_PEERCRED:
{
struct ucred peercred;

1
net/mptcp/sockopt.c
View file

@ -355,6 +355,7 @@ static int mptcp_setsockopt_sol_socket(struct mptcp_sock *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:

18
net/unix/af_unix.c
View file

@ -1361,7 +1361,8 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
if (err)
goto out;
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 = unix_autobind(sk);
if (err)
@ -1469,7 +1470,8 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
if (err)
goto out;
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 = unix_autobind(sk);
if (err)
goto out;
@ -1670,6 +1672,8 @@ static void unix_sock_inherit_flags(const struct socket *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 socket *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);
}
/*
@ -1904,7 +1910,8 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
goto out;
}
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 = unix_autobind(sk);
if (err)
goto out;
@ -2718,7 +2725,8 @@ static int unix_stream_read_generic(struct unix_stream_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);

2
tools/include/uapi/asm-generic/socket.h
View file

@ -121,6 +121,8 @@
#define SO_RCVMARK 75
#define SO_PASSPIDFD 76
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))