# Re: \[PATCH 07/10\] net: add SO\_PEERPIDFD\_THREAD to get a thread-specific pidfd - From: Alexander Mikhalitsyn \ - Date: 2026-09-07 10:50:02 - List: netdev - Page: https://ratatoskr.run/netdev/2026/09/17524423 - Thread: https://ratatoskr.run/netdev/2026/08/17483571/t.md ```text Am Mo., 31. Aug. 2026 um 13:21 Uhr schrieb Christian Brauner [ref]: > > SO_PEERPIDFD hands out a pidfd for the thread-group that called > connect() or socketpair(). Enable workloads such as the coredump server > or a broker to get a pidfd of the specific thread that connected to the > socket. > > Signed-off-by: Christian Brauner (Amutable) LGTM Reviewed-by: Alexander Mikhalitsyn > --- > 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/uapi/asm-generic/socket.h | 2 + > net/core/sock.c | 87 ++++++++++++++++++++--------------- > net/unix/af_unix.c | 1 + > 7 files changed, 61 insertions(+), 37 deletions(-) > > diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h > index bb3d534826bb..5d3524c26b2b 100644 > --- a/arch/alpha/include/uapi/asm/socket.h > +++ b/arch/alpha/include/uapi/asm/socket.h > @@ -159,6 +159,8 @@ > > #define SO_PASSPIDFD_THREAD 86 > > +#define SO_PEERPIDFD_THREAD 87 > + > #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 269badcaa086..245a43f52fb1 100644 > --- a/arch/mips/include/uapi/asm/socket.h > +++ b/arch/mips/include/uapi/asm/socket.h > @@ -170,6 +170,8 @@ > > #define SO_PASSPIDFD_THREAD 86 > > +#define SO_PEERPIDFD_THREAD 87 > + > #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 313aee10a52c..f23710e1c671 100644 > --- a/arch/parisc/include/uapi/asm/socket.h > +++ b/arch/parisc/include/uapi/asm/socket.h > @@ -151,6 +151,8 @@ > > #define SO_PASSPIDFD_THREAD 0x4054 > > +#define SO_PEERPIDFD_THREAD 0x4055 > + > #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 bd3e69bcce7a..b35b25bdefc2 100644 > --- a/arch/sparc/include/uapi/asm/socket.h > +++ b/arch/sparc/include/uapi/asm/socket.h > @@ -152,6 +152,8 @@ > > #define SO_PASSPIDFD_THREAD 0x005f > > +#define SO_PEERPIDFD_THREAD 0x0060 > + > #if !defined(__KERNEL__) > > > diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h > index d1e5c6de146d..56fed7ab27ab 100644 > --- a/include/uapi/asm-generic/socket.h > +++ b/include/uapi/asm-generic/socket.h > @@ -154,6 +154,8 @@ > > #define SO_PASSPIDFD_THREAD 86 > > +#define SO_PEERPIDFD_THREAD 87 > + > #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 6ada7e7eb7d7..cb2ffd329bc6 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -1743,6 +1743,50 @@ static int groups_to_user(sockptr_t dst, const struct group_info *src) > return 0; > } > > +/* Hand out a pidfd for @type of the socket's peer via SO_PEERPIDFD*. */ > +static int sk_getsockopt_peerpidfd(struct sock *sk, enum pid_type type, > + sockptr_t optval, sockptr_t optlen, int len) > +{ > + struct file *pidfd_file = NULL; > + unsigned int flags = 0; > + struct pid *peer_pid; > + int pidfd; > + > + if (len > sizeof(pidfd)) > + len = sizeof(pidfd); > + > + spin_lock(&sk->sk_peer_lock); > + peer_pid = get_pid(sk->sk_peer_pid[type]); > + spin_unlock(&sk->sk_peer_lock); > + > + if (!peer_pid) > + return -ENODATA; > + > + /* The use of PIDFD_STALE requires stashing of struct pid on pidfs > + * with pidfs_register_pid() and only AF_UNIX were prepared for this. > + */ > + if (sk->sk_family == AF_UNIX) > + flags |= PIDFD_STALE; > + if (type == PIDTYPE_PID) > + flags |= PIDFD_THREAD; > + > + pidfd = pidfd_prepare(peer_pid, flags, &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))) { > + put_unused_fd(pidfd); > + fput(pidfd_file); > + > + return -EFAULT; > + } > + > + fd_install(pidfd, pidfd_file); > + return 0; > +} > + > int sk_getsockopt(struct sock *sk, int level, int optname, > sockptr_t optval, sockptr_t optlen) > { > @@ -1938,45 +1982,14 @@ int sk_getsockopt(struct sock *sk, int level, int optname, > } > > case SO_PEERPIDFD: > - { > - struct pid *peer_pid; > - struct file *pidfd_file = NULL; > - unsigned int flags = 0; > - int pidfd; > - > - if (len > sizeof(pidfd)) > - len = sizeof(pidfd); > - > - spin_lock(&sk->sk_peer_lock); > - peer_pid = get_pid(sk->sk_peer_pid[PIDTYPE_TGID]); > - spin_unlock(&sk->sk_peer_lock); > - > - if (!peer_pid) > - return -ENODATA; > - > - /* The use of PIDFD_STALE requires stashing of struct pid > - * on pidfs with pidfs_register_pid() and only AF_UNIX > - * were prepared for this. > - */ > - if (sk->sk_family == AF_UNIX) > - flags = PIDFD_STALE; > + return sk_getsockopt_peerpidfd(sk, PIDTYPE_TGID, optval, optlen, len); > > - pidfd = pidfd_prepare(peer_pid, flags, &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))) { > - put_unused_fd(pidfd); > - fput(pidfd_file); > - > - return -EFAULT; > - } > + case SO_PEERPIDFD_THREAD: > + /* Only AF_UNIX records the peer's connecting thread. */ > + if (!sk_is_unix(sk)) > + return -EOPNOTSUPP; > > - fd_install(pidfd, pidfd_file); > - return 0; > - } > + return sk_getsockopt_peerpidfd(sk, PIDTYPE_PID, optval, optlen, len); > > case SO_PEERGROUPS: > { > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > index d01ee76c8026..563d9827c5cc 100644 > --- a/net/unix/af_unix.c > +++ b/net/unix/af_unix.c > @@ -1056,6 +1056,7 @@ static bool unix_bpf_bypass_getsockopt(int level, int optname) > if (level == SOL_SOCKET) { > switch (optname) { > case SO_PEERPIDFD: > + case SO_PEERPIDFD_THREAD: > return true; > default: > return false; > > -- > 2.53.0 > ```