From 73df96d47c0a83e272643e8b1273805ee6983dec Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Thu, 24 Oct 2024 17:37:03 +0000
Subject: [PATCH] Stop leaking kernel stack guard pages.

ok mpi@, anton@
---
 sys/arch/amd64/amd64/vm_machdep.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/sys/arch/amd64/amd64/vm_machdep.c b/sys/arch/amd64/amd64/vm_machdep.c
index 5275969ed39..5fa53922735 100644
--- a/sys/arch/amd64/amd64/vm_machdep.c
+++ b/sys/arch/amd64/amd64/vm_machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vm_machdep.c,v 1.48 2024/10/21 18:27:34 kettenis Exp $	*/
+/*	$OpenBSD: vm_machdep.c,v 1.49 2024/10/24 17:37:03 kettenis Exp $	*/
 /*	$NetBSD: vm_machdep.c,v 1.1 2003/04/26 18:39:33 fvdl Exp $	*/
 
 /*-
@@ -135,8 +135,16 @@ cpu_exit(struct proc *p)
 void
 setguardpage(struct proc *p)
 {
-	pmap_kremove((vaddr_t)p->p_addr + PAGE_SIZE, PAGE_SIZE);
+	struct vm_page *pg = NULL;
+	vaddr_t va = (vaddr_t)p->p_addr + PAGE_SIZE;
+	paddr_t pa;
+
+	if (pmap_extract(pmap_kernel(), va, &pa))
+		pg = PHYS_TO_VM_PAGE(pa);
+	pmap_kremove(va, PAGE_SIZE);
 	pmap_update(pmap_kernel());
+	if (pg)
+		uvm_pagefree(pg);
 }
 
 struct kmem_va_mode kv_physwait = {
-- 
2.20.1