From: Christian Brauner <brauner@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>,
Kuniyuki Iwashima <kuniyu@google.com>,
Oleg Nesterov <oleg@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Willem de Bruijn <willemb@google.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jan Kara <jack@suse.cz>,
linux-fsdevel@vger.kernel.org,
Alexander Mikhalitsyn <alexander@mihalicyn.com>,
"Christian Brauner (Amutable)" <brauner@kernel.org>
Subject: [PATCH v2 02/10] af_unix: record the pid of the sending thread
Date: Wed, 09 Sep 2026 12:43:01 +0200 [thread overview]
Message-ID: <20260909-work-unix-passpidfd-v2-2-7bd342abb2d1@kernel.org> (raw)
In-Reply-To: <20260909-work-unix-passpidfd-v2-0-7bd342abb2d1@kernel.org>
Currently only the struct pid of the thread-group leader is recorded.
The identity of the actual thread that sent the message or is connected
to a given socket cannot be retrieved.
Add the plumbing to make it possible to retrieve a pidfd for the sender.
Nothing uses the thread-specific struct pid yet. No functional changes.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
include/net/scm.h | 7 +++----
net/core/scm.c | 21 +++++++++++++++++----
net/unix/af_unix.c | 23 +++++++++++++----------
net/unix/af_unix.h | 3 ++-
4 files changed, 35 insertions(+), 19 deletions(-)
diff --git a/include/net/scm.h b/include/net/scm.h
index 86ae6bc109ec..aa7d15c5fc27 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -42,7 +42,7 @@ struct scm_fp_list {
};
struct scm_cookie {
- struct pid *pid; /* Skb credentials */
+ DECLARE_PIDS(pid, PIDTYPE_TGID); /* Skb credentials by pid type */
struct scm_fp_list *fp; /* Passed files */
struct scm_creds creds; /* Skb credentials */
#ifdef CONFIG_SECURITY_NETWORK
@@ -69,7 +69,7 @@ static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_co
static __inline__ void scm_set_cred(struct scm_cookie *scm,
struct pid *pid, kuid_t uid, kgid_t gid)
{
- scm->pid = get_pid(pid);
+ scm->pid[PIDTYPE_TGID] = get_pid(pid);
scm->creds.pid = pid_vnr(pid);
scm->creds.uid = uid;
scm->creds.gid = gid;
@@ -77,8 +77,7 @@ static __inline__ void scm_set_cred(struct scm_cookie *scm,
static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
{
- put_pid(scm->pid);
- scm->pid = NULL;
+ put_pids(scm->pid);
}
static __inline__ void scm_destroy(struct scm_cookie *scm)
diff --git a/net/core/scm.c b/net/core/scm.c
index f0d44ecdb11f..9b9e119c353a 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -149,6 +149,7 @@ EXPORT_SYMBOL(__scm_destroy);
static inline int scm_replace_pid(struct scm_cookie *scm, struct pid *pid)
{
+ struct pid *thread_pid;
int err;
/* drop all previous references */
@@ -158,7 +159,18 @@ static inline int scm_replace_pid(struct scm_cookie *scm, struct pid *pid)
if (unlikely(err))
return err;
- scm->pid = pid;
+ /* A sender naming its own thread-group sends from the current thread. */
+ if (pid == task_tgid(current))
+ thread_pid = task_pid(current);
+ else
+ thread_pid = pid;
+
+ err = pidfs_register_pid(thread_pid);
+ if (unlikely(err))
+ return err;
+
+ scm->pid[PIDTYPE_TGID] = pid;
+ scm->pid[PIDTYPE_PID] = get_pid(thread_pid);
scm->creds.pid = pid_vnr(pid);
return 0;
}
@@ -207,7 +219,8 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p)
if (err)
goto error;
- if (!p->pid || pid_vnr(p->pid) != creds.pid) {
+ if (!p->pid[PIDTYPE_TGID] ||
+ pid_vnr(p->pid[PIDTYPE_TGID]) != creds.pid) {
struct pid *pid;
err = -ESRCH;
pid = find_get_pid(creds.pid);
@@ -504,10 +517,10 @@ static void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm)
return;
}
- if (!scm->pid)
+ if (!scm->pid[PIDTYPE_TGID])
return;
- pidfd = pidfd_prepare(scm->pid, PIDFD_STALE, &pidfd_file);
+ pidfd = pidfd_prepare(scm->pid[PIDTYPE_TGID], PIDFD_STALE, &pidfd_file);
if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) {
if (pidfd_file) {
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 13f9926bf205..011af84e3626 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1973,7 +1973,7 @@ static void unix_destruct_scm(struct sk_buff *skb)
{
struct scm_cookie scm = {};
- swap(scm.pid, UNIXCB(skb).pid);
+ swap_pids(scm.pid, UNIXCB(skb).pid);
if (UNIXCB(skb).fp)
unix_detach_fds(&scm, skb);
@@ -1991,7 +1991,7 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen
{
int err = 0;
- UNIXCB(skb).pid = get_pid(scm->pid);
+ get_pids(UNIXCB(skb).pid, scm->pid);
UNIXCB(skb).uid = scm->creds.uid;
UNIXCB(skb).gid = scm->creds.gid;
UNIXCB(skb).fp = NULL;
@@ -2005,7 +2005,10 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen
static void unix_skb_to_scm(struct sk_buff *skb, struct scm_cookie *scm)
{
- scm_set_cred(scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
+ get_pids(scm->pid, UNIXCB(skb).pid);
+ scm->creds.pid = pid_vnr(scm->pid[PIDTYPE_TGID]);
+ scm->creds.uid = UNIXCB(skb).uid;
+ scm->creds.gid = UNIXCB(skb).gid;
unix_set_secdata(scm, skb);
}
@@ -2025,20 +2028,20 @@ static void unix_skb_to_scm(struct sk_buff *skb, struct scm_cookie *scm)
static int unix_maybe_add_creds(struct sk_buff *skb, const struct sock *sk,
const struct sock *other)
{
- if (UNIXCB(skb).pid)
+ if (UNIXCB(skb).pid[PIDTYPE_TGID])
return 0;
if (unix_may_passcred(sk) || unix_may_passcred(other) ||
!other->sk_socket) {
- struct pid *pid;
int err;
- pid = task_tgid(current);
- err = pidfs_register_pid(pid);
- if (unlikely(err))
+ get_task_pids(UNIXCB(skb).pid, current);
+ err = pidfs_register_pids(UNIXCB(skb).pid);
+ if (unlikely(err)) {
+ put_pids(UNIXCB(skb).pid);
return err;
+ }
- UNIXCB(skb).pid = get_pid(pid);
current_uid_gid(&UNIXCB(skb).uid, &UNIXCB(skb).gid);
}
@@ -2048,7 +2051,7 @@ static int unix_maybe_add_creds(struct sk_buff *skb, const struct sock *sk,
static bool unix_skb_scm_eq(struct sk_buff *skb,
struct scm_cookie *scm)
{
- return UNIXCB(skb).pid == scm->pid &&
+ return UNIXCB(skb).pid[PIDTYPE_TGID] == scm->pid[PIDTYPE_TGID] &&
uid_eq(UNIXCB(skb).uid, scm->creds.uid) &&
gid_eq(UNIXCB(skb).gid, scm->creds.gid) &&
unix_secdata_eq(scm, skb);
diff --git a/net/unix/af_unix.h b/net/unix/af_unix.h
index 8119dbeef3a3..402742895acc 100644
--- a/net/unix/af_unix.h
+++ b/net/unix/af_unix.h
@@ -2,6 +2,7 @@
#ifndef __AF_UNIX_H
#define __AF_UNIX_H
+#include <linux/pid_types.h>
#include <linux/uidgid.h>
#define UNIX_HASH_MOD (256 - 1)
@@ -11,7 +12,7 @@
struct sock *unix_peer_get(struct sock *sk);
struct unix_skb_parms {
- struct pid *pid; /* skb credentials */
+ DECLARE_PIDS(pid, PIDTYPE_TGID); /* skb credentials by pid type */
kuid_t uid;
kgid_t gid;
struct scm_fp_list *fp; /* Passed files */
--
2.53.0
next prev parent reply other threads:[~2026-09-09 10:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-09 10:42 [PATCH v2 00/10] net: support thread-specific pidfds for send and connect Christian Brauner
2026-09-09 10:43 ` [PATCH v2 01/10] pid: add helpers to operate on a struct pid array Christian Brauner
2026-09-10 4:14 ` Kuniyuki Iwashima
2026-09-09 10:43 ` Christian Brauner [this message]
2026-09-09 10:43 ` [PATCH v2 03/10] net: add SO_PASSPIDFD_THREAD to get a thread-specific SCM_PIDFD Christian Brauner
2026-09-10 5:24 ` Kuniyuki Iwashima
2026-09-09 10:43 ` [PATCH v2 04/10] selftests/net: SO_PASSPIDFD_THREAD Christian Brauner
2026-09-09 10:43 ` [PATCH v2 05/10] net: turn sk_peer_pid into an array indexed by pid type Christian Brauner
2026-09-09 10:43 ` [PATCH v2 06/10] af_unix: record the pid of the connecting thread Christian Brauner
2026-09-09 10:43 ` [PATCH v2 07/10] net: add SO_PEERPIDFD_THREAD to get a thread-specific pidfd Christian Brauner
2026-09-10 6:11 ` Kuniyuki Iwashima
2026-09-09 10:43 ` [PATCH v2 08/10] selftests/net: SO_PEERPIDFD_THREAD Christian Brauner
2026-09-09 10:43 ` [PATCH v2 09/10] pidfs: record the coredump on the dumping thread's pid too Christian Brauner
2026-09-09 10:43 ` [PATCH v2 10/10] selftests/coredump: check the dumping thread's pidfd Christian Brauner
2026-09-09 11:10 ` [PATCH v2 00/10] net: support thread-specific pidfds for send and connect Alexander Mikhalitsyn
2026-09-09 12:40 ` Christian Brauner
2026-09-09 18:39 ` Jakub Kicinski
2026-09-10 6:33 ` Kuniyuki Iwashima
2026-09-10 7:54 ` Christian Brauner
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