On Tue, Apr 11, 2023 at 12:42:30PM +0200, Alexander Mikhalitsyn wrote:
> Add SO_PEERPIDFD which allows to get pidfd of peer socket holder pidfd.
> This thing is direct analog of SO_PEERCRED which allows to get plain PID.
>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: Leon Romanovsky <leon@xxxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> Cc: Lennart Poettering <mzxreary@xxxxxxxxxxx>
> Cc: Luca Boccassi <bluca@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-arch@xxxxxxxxxxxxxxx
> Tested-by: Luca Boccassi <bluca@xxxxxxxxxx>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
> ---
> v3:
> - fixed possible fd leak (thanks to Christian Brauner)
> v2:
> According to review comments from Kuniyuki Iwashima and Christian Brauner:
> - use pidfd_create(..) retval as a result
> - whitespace change
> ---
> arch/alpha/include/uapi/asm/socket.h | 1 +
> arch/mips/include/uapi/asm/socket.h | 1 +
> arch/parisc/include/uapi/asm/socket.h | 1 +
> arch/sparc/include/uapi/asm/socket.h | 1 +
> include/uapi/asm-generic/socket.h | 1 +
> net/core/sock.c | 33 +++++++++++++++++++++++++
> net/socket.c | 7 ++++++
> tools/include/uapi/asm-generic/socket.h | 1 +
> 8 files changed, 46 insertions(+)
>
> diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> index ff310613ae64..e94f621903fe 100644
> --- a/arch/alpha/include/uapi/asm/socket.h
> +++ b/arch/alpha/include/uapi/asm/socket.h
> @@ -138,6 +138,7 @@
> #define SO_RCVMARK 75
>
> #define SO_PASSPIDFD 76
> +#define SO_PEERPIDFD 77
>
> #if !defined(__KERNEL__)
>
> diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
> index 762dcb80e4ec..60ebaed28a4c 100644
> --- a/arch/mips/include/uapi/asm/socket.h
> +++ b/arch/mips/include/uapi/asm/socket.h
> @@ -149,6 +149,7 @@
> #define SO_RCVMARK 75
>
> #define SO_PASSPIDFD 76
> +#define SO_PEERPIDFD 77
>
> #if !defined(__KERNEL__)
>
> diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
> index df16a3e16d64..be264c2b1a11 100644
> --- a/arch/parisc/include/uapi/asm/socket.h
> +++ b/arch/parisc/include/uapi/asm/socket.h
> @@ -130,6 +130,7 @@
> #define SO_RCVMARK 0x4049
>
> #define SO_PASSPIDFD 0x404A
> +#define SO_PEERPIDFD 0x404B
>
> #if !defined(__KERNEL__)
>
> diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
> index 6e2847804fea..682da3714686 100644
> --- a/arch/sparc/include/uapi/asm/socket.h
> +++ b/arch/sparc/include/uapi/asm/socket.h
> @@ -131,6 +131,7 @@
> #define SO_RCVMARK 0x0054
>
> #define SO_PASSPIDFD 0x0055
> +#define SO_PEERPIDFD 0x0056
>
> #if !defined(__KERNEL__)
>
> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> index b76169fdb80b..8ce8a39a1e5f 100644
> --- a/include/uapi/asm-generic/socket.h
> +++ b/include/uapi/asm-generic/socket.h
> @@ -133,6 +133,7 @@
> #define SO_RCVMARK 75
>
> #define SO_PASSPIDFD 76
> +#define SO_PEERPIDFD 77
>
> #if !defined(__KERNEL__)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 3f974246ba3e..2b040a69e355 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1763,6 +1763,39 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
> goto lenout;
> }
>
> + case SO_PEERPIDFD:
> + {
> + struct pid *peer_pid;
> + struct file *pidfd_file = NULL;
> + int pidfd;
> +
> + if (len > sizeof(pidfd))
> + len = sizeof(pidfd);
> +
> + spin_lock(&sk->sk_peer_lock);
> + peer_pid = get_pid(sk->sk_peer_pid);
> + spin_unlock(&sk->sk_peer_lock);
> +
> + pidfd = pidfd_prepare(peer_pid, 0, &pidfd_file);
> +
> + put_pid(peer_pid);
Would be a bit nicer if this would be:
pidfd = pidfd_prepare(peer_pid, 0, &pidfd_file);
put_pid(peer_pid);
if (pidfd < 0)
return pidfd;
if (copy_to_sockptr(optval, &pidfd, len) ||
copy_to_sockptr(optlen, &len, sizeof(int)))
return -EFAULT;
fd_install(pidfd, pidfd_file);
return 0;
Otherwise seems good enough to me.
> +
> + if (copy_to_sockptr(optval, &pidfd, len) ||
> + copy_to_sockptr(optlen, &len, sizeof(int))) {
> + if (pidfd >= 0) {
> + put_unused_fd(pidfd);
> + fput(pidfd_file);
> + }
> +
> + return -EFAULT;
> + }
> +
> + if (pidfd_file)
> + fd_install(pidfd, pidfd_file);
> +
> + return 0;
> + }
> +
> case SO_PEERGROUPS:
> {
> const struct cred *cred;
> diff --git a/net/socket.c b/net/socket.c
> index 9c1ef11de23f..505b85489354 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2248,6 +2248,13 @@ static bool sockopt_installs_fd(int level, int optname)
> default:
> return false;
> }
> + } else if (level == SOL_SOCKET) {
> + switch (optname) {
> + case SO_PEERPIDFD:
> + return true;
> + default:
> + return false;
> + }
> }
>
> return false;
> diff --git a/tools/include/uapi/asm-generic/socket.h b/tools/include/uapi/asm-generic/socket.h
> index fbbc4bf53ee3..54d9c8bf7c55 100644
> --- a/tools/include/uapi/asm-generic/socket.h
> +++ b/tools/include/uapi/asm-generic/socket.h
> @@ -122,6 +122,7 @@
> #define SO_RCVMARK 75
>
> #define SO_PASSPIDFD 76
> +#define SO_PEERPIDFD 77
>
> #if !defined(__KERNEL__)
>
> --
> 2.34.1
>
