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Date: Thu, 16 Mar 2023 22:53:20 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <aleksandr.mikhalitsyn@...onical.com>
CC: <arnd@...db.de>, <brauner@...nel.org>, <davem@...emloft.net>,
<dsahern@...nel.org>, <edumazet@...gle.com>,
<keescook@...omium.org>, <kuba@...nel.org>, <leon@...nel.org>,
<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<netdev@...r.kernel.org>, <pabeni@...hat.com>, <kuniyu@...zon.com>
Subject: Re: [PATCH net-next 1/3] scm: add SO_PASSPIDFD and SCM_PIDFD
From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Date: Thu, 16 Mar 2023 14:15:24 +0100
> 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.
>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> Cc: netdev@...r.kernel.org
> Cc: linux-arch@...r.kernel.org
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> ---
> 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 | 16 +++++++++++++++-
> 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, 54 insertions(+), 6 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 @@
>
> #define SO_RCVMARK 75
>
> +#define SO_PASSPIDFD 76
> +
> #if !defined(__KERNEL__)
>
> #if __BITS_PER_LONG == 64
> diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/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 @@
>
> #define SO_RCVMARK 75
>
> +#define SO_PASSPIDFD 76
> +
> #if !defined(__KERNEL__)
>
> #if __BITS_PER_LONG == 64
> diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/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 @@
>
> #define SO_RCVMARK 0x4049
>
> +#define SO_PASSPIDFD 0x404A
> +
> #if !defined(__KERNEL__)
>
> #if __BITS_PER_LONG == 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 @@
>
> #define SO_RCVMARK 0x0054
>
> +#define SO_PASSPIDFD 0x0055
> +
> #if !defined(__KERNEL__)
>
>
> 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
>
> #ifndef ARCH_HAS_SOCKET_TYPES
> /**
> diff --git a/include/linux/socket.h b/include/linux/socket.h
> index 13c3a237b9c9..6bf90f251910 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) */
>
> struct ucred {
> __u32 pid;
> diff --git a/include/net/scm.h b/include/net/scm.h
> index 585adc1346bd..4617fbc65294 100644
> --- a/include/net/scm.h
> +++ b/include/net/scm.h
> @@ -124,7 +124,9 @@ 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 ||
> + if (test_bit(SOCK_PASSCRED, &sock->flags) ||
> + test_bit(SOCK_PASSPIDFD, &sock->flags) ||
> + scm->fp ||
nit: I'd remove newline here.
> scm_has_secdata(sock))
> msg->msg_flags |= MSG_CTRUNC;
> scm_destroy(scm);
> @@ -141,6 +143,18 @@ 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)) {
> + int pidfd;
> +
> + if (WARN_ON_ONCE(!scm->pid) ||
> + !pid_has_task(scm->pid, PIDTYPE_TGID))
Can we change pidfd_create() to return -ESRCH as it has the same test ?
> + pidfd = -ESRCH;
> + else
> + pidfd = pidfd_create(scm->pid, 0);
Then we can change this part like:
int pidfd = pidfd_create(scm->pid, 0);
WARN_ON_ONCE(!scm->pid);
Thanks,
Kuniyuki
> +
> + put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd);
> + }
> +
> scm_destroy_cred(scm);
>
> scm_passec(sock, msg, scm);
> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> index 638230899e98..b76169fdb80b 100644
> --- a/include/uapi/asm-generic/socket.h
> +++ b/include/uapi/asm-generic/socket.h
> @@ -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__))
> diff --git a/net/core/sock.c b/net/core/sock.c
> index c25888795390..3f974246ba3e 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -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:
> @@ -1737,6 +1744,10 @@ 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;
> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> index 8a9656248b0f..bd80e707d0b3 100644
> --- a/net/mptcp/sockopt.c
> +++ b/net/mptcp/sockopt.c
> @@ -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:
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 0b0f18ecce44..b0ac768752fa 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, 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);
> }
>
> /*
> @@ -1922,7 +1928,8 @@ 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;
> @@ -2824,7 +2831,8 @@ 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);
> diff --git a/tools/include/uapi/asm-generic/socket.h b/tools/include/uapi/asm-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 @@
>
> #define SO_RCVMARK 75
>
> +#define SO_PASSPIDFD 76
> +
> #if !defined(__KERNEL__)
>
> #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
> --
> 2.34.1
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