[PATCH v2 06/10] af_unix: record the pid of the connecting thread

[Christian Brauner <brauner@kernel.org>]

Currently only the struct pid of the thread-group leader is recorded.
The identity of the actual thread that connected to a given socket
cannot be retrieved.

Add the plumbing to make it possible to retrieve a pidfd for the
connecting thread. Nothing uses the thread-specific struct pid yet. No
functional changes.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 net/unix/af_unix.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 335abd23c9bf..d01ee76c8026 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -743,51 +743,47 @@ struct unix_peercred {
 
 static inline int prepare_peercred(struct unix_peercred *peercred)
 {
-	struct pid *pid;
 	int err;
 
-	pid = task_tgid(current);
-	err = pidfs_register_pid(pid);
-	if (likely(!err)) {
-		peercred->peer_pid[PIDTYPE_TGID] = get_pid(pid);
-		peercred->peer_cred = get_current_cred();
+	get_task_pids(peercred->peer_pid, current);
+	err = pidfs_register_pids(peercred->peer_pid);
+	if (unlikely(err)) {
+		put_pids(peercred->peer_pid);
+		return err;
 	}
-	return err;
+
+	peercred->peer_cred = get_current_cred();
+	return 0;
 }
 
 static void drop_peercred(struct unix_peercred *peercred)
 {
 	const struct cred *cred = NULL;
-	struct pid *pid = NULL;
 
 	might_sleep();
 
-	swap(peercred->peer_pid[PIDTYPE_TGID], pid);
+	put_pids(peercred->peer_pid);
 	swap(peercred->peer_cred, cred);
-
-	put_pid(pid);
 	put_cred(cred);
 }
 
 static inline void init_peercred(struct sock *sk,
 				 const struct unix_peercred *peercred)
 {
-	sk->sk_peer_pid[PIDTYPE_TGID] = peercred->peer_pid[PIDTYPE_TGID];
+	memcpy(sk->sk_peer_pid, peercred->peer_pid, sizeof(sk->sk_peer_pid));
 	sk->sk_peer_cred = peercred->peer_cred;
 }
 
 static void update_peercred(struct sock *sk, struct unix_peercred *peercred)
 {
 	const struct cred *old_cred;
-	struct pid *old_pid;
 
 	spin_lock(&sk->sk_peer_lock);
-	old_pid = sk->sk_peer_pid[PIDTYPE_TGID];
+	swap_pids(sk->sk_peer_pid, peercred->peer_pid);
 	old_cred = sk->sk_peer_cred;
-	init_peercred(sk, peercred);
+	sk->sk_peer_cred = peercred->peer_cred;
 	spin_unlock(&sk->sk_peer_lock);
 
-	peercred->peer_pid[PIDTYPE_TGID] = old_pid;
 	peercred->peer_cred = old_cred;
 }
 
@@ -796,7 +792,7 @@ static void copy_peercred(struct sock *sk, struct sock *peersk)
 	lockdep_assert_held(&unix_sk(peersk)->lock);
 
 	spin_lock(&sk->sk_peer_lock);
-	sk->sk_peer_pid[PIDTYPE_TGID] = get_pid(peersk->sk_peer_pid[PIDTYPE_TGID]);
+	get_pids(sk->sk_peer_pid, peersk->sk_peer_pid);
 	sk->sk_peer_cred = get_cred(peersk->sk_peer_cred);
 	spin_unlock(&sk->sk_peer_lock);
 }

-- 
2.53.0