From 86c583514576a3099d79bc4601e2fc7824fe054f Mon Sep 17 00:00:00 2001
From: mpi <mpi@openbsd.org>
Date: Mon, 15 Feb 2021 09:35:59 +0000
Subject: [PATCH] Move single_thread_set() out of KERNEL_LOCK().

Use the SCHED_LOCK() to ensure `ps_thread' isn't being modified by a sibling
when entering tsleep(9) w/o KERNEL_LOCK().

ok visa@
---
 sys/kern/kern_exit.c | 5 ++++-
 sys/kern/kern_fork.c | 6 +++---
 sys/kern/kern_sig.c  | 7 +------
 sys/sys/proc.h       | 4 ++--
 4 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index 94e3981151f..cbb116e6dcc 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_exit.c,v 1.195 2021/02/08 10:51:01 mpi Exp $	*/
+/*	$OpenBSD: kern_exit.c,v 1.196 2021/02/15 09:35:59 mpi Exp $	*/
 /*	$NetBSD: kern_exit.c,v 1.39 1996/04/22 01:38:25 christos Exp $	*/
 
 /*
@@ -124,6 +124,7 @@ exit1(struct proc *p, int xexit, int xsig, int flags)
 {
 	struct process *pr, *qr, *nqr;
 	struct rusage *rup;
+	int s;
 
 	atomic_setbits_int(&p->p_flag, P_WEXIT);
 
@@ -161,7 +162,9 @@ exit1(struct proc *p, int xexit, int xsig, int flags)
 	}
 
 	/* unlink ourselves from the active threads */
+	SCHED_LOCK(s);
 	TAILQ_REMOVE(&pr->ps_threads, p, p_thr_link);
+	SCHED_UNLOCK(s);
 	if ((p->p_flag & P_THREAD) == 0) {
 		/* main thread gotta wait because it has the pid, et al */
 		while (pr->ps_refcnt > 1)
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index ee11b705d8f..2c84a9abf52 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_fork.c,v 1.233 2021/02/11 13:40:28 otto Exp $	*/
+/*	$OpenBSD: kern_fork.c,v 1.234 2021/02/15 09:35:59 mpi Exp $	*/
 /*	$NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $	*/
 
 /*
@@ -558,13 +558,13 @@ thread_fork(struct proc *curp, void *stack, void *tcb, pid_t *tidptr,
 
 	LIST_INSERT_HEAD(&allproc, p, p_list);
 	LIST_INSERT_HEAD(TIDHASH(p->p_tid), p, p_hash);
-	TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link);
 
+	SCHED_LOCK(s);
+	TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link);
 	/*
 	 * if somebody else wants to take us to single threaded mode,
 	 * count ourselves in.
 	 */
-	SCHED_LOCK(s);
 	if (pr->ps_single) {
 		atomic_inc_int(&pr->ps_singlecount);
 		atomic_setbits_int(&p->p_flag, P_SUSPSINGLE);
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 6435794c833..97d99967826 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_sig.c,v 1.272 2021/02/08 10:51:01 mpi Exp $	*/
+/*	$OpenBSD: kern_sig.c,v 1.273 2021/02/15 09:35:59 mpi Exp $	*/
 /*	$NetBSD: kern_sig.c,v 1.54 1996/04/22 01:38:32 christos Exp $	*/
 
 /*
@@ -1209,11 +1209,7 @@ issignal(struct proc *p)
 		    signum != SIGKILL) {
 			pr->ps_xsig = signum;
 
-			if (dolock)
-				KERNEL_LOCK();
 			single_thread_set(p, SINGLE_PTRACE, 0);
-			if (dolock)
-				KERNEL_UNLOCK();
 
 			if (dolock)
 				SCHED_LOCK(s);
@@ -2009,7 +2005,6 @@ single_thread_set(struct proc *p, enum single_thread_mode mode, int deep)
 	struct proc *q;
 	int error, s;
 
-	KERNEL_ASSERT_LOCKED();
 	KASSERT(curproc == p);
 
 	SCHED_LOCK(s);
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 43178052472..462af504f33 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: proc.h,v 1.308 2021/02/08 10:51:02 mpi Exp $	*/
+/*	$OpenBSD: proc.h,v 1.309 2021/02/15 09:35:59 mpi Exp $	*/
 /*	$NetBSD: proc.h,v 1.44 1996/04/22 01:23:21 christos Exp $	*/
 
 /*-
@@ -167,7 +167,7 @@ struct process {
 	struct	ucred *ps_ucred;	/* Process owner's identity. */
 
 	LIST_ENTRY(process) ps_list;	/* List of all processes. */
-	TAILQ_HEAD(,proc) ps_threads;	/* Threads in this process. */
+	TAILQ_HEAD(,proc) ps_threads;	/* [K|S] Threads in this process. */
 
 	LIST_ENTRY(process) ps_pglist;	/* List of processes in pgrp. */
 	struct	process *ps_pptr; 	/* Pointer to parent process. */
-- 
2.20.1