From df4e817b710809425d899340dbfa8504a3ca4ba5 Mon Sep 17 00:00:00 2001
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Date: Fri, 14 Jan 2022 14:06:37 -0800
Subject: mm: page table check

Check user page table entries at the time they are added and removed.

Allows to synchronously catch memory corruption issues related to double
mapping.

When a pte for an anonymous page is added into page table, we verify
that this pte does not already point to a file backed page, and vice
versa if this is a file backed page that is being added we verify that
this page does not have an anonymous mapping

We also enforce that read-only sharing for anonymous pages is allowed
(i.e.  cow after fork).  All other sharing must be for file pages.

Page table check allows to protect and debug cases where "struct page"
metadata became corrupted for some reason.  For example, when refcnt or
mapcount become invalid.

Link: https://lkml.kernel.org/r/20211221154650.1047963-4-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Xu <weixugc@google.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/page_ext.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'mm/page_ext.c')

diff --git a/mm/page_ext.c b/mm/page_ext.c
index 6242afb24d84..bee3240604dc 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -8,6 +8,7 @@
 #include <linux/kmemleak.h>
 #include <linux/page_owner.h>
 #include <linux/page_idle.h>
+#include <linux/page_table_check.h>
 
 /*
  * struct page extension
@@ -75,6 +76,9 @@ static struct page_ext_operations *page_ext_ops[] = {
 #if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
 	&page_idle_ops,
 #endif
+#ifdef CONFIG_PAGE_TABLE_CHECK
+	&page_table_check_ops,
+#endif
 };
 
 unsigned long page_ext_size = sizeof(struct page_ext);
-- 
cgit v1.2.3


From cab0a7c115546a4865fb7439558af9077a569574 Mon Sep 17 00:00:00 2001
From: Ting Liu <liuting.0x7c00@bytedance.com>
Date: Fri, 14 Jan 2022 14:09:28 -0800
Subject: mm: make some vars and functions static or __init

"page_idle_ops" as a global var, but its scope of use within this
document.  So it should be static.

"page_ext_ops" is a var used in the kernel initial phase.  And other
functions are aslo used in the kernel initial phase.  So they should be
__init or __initdata to reclaim memory.

Link: https://lkml.kernel.org/r/20211217095023.67293-1-liuting.0x7c00@bytedance.com
Signed-off-by: Ting Liu <liuting.0x7c00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/page_ext.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'mm/page_ext.c')

diff --git a/mm/page_ext.c b/mm/page_ext.c
index bee3240604dc..2e66d934d63f 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -64,12 +64,12 @@ static bool need_page_idle(void)
 {
 	return true;
 }
-struct page_ext_operations page_idle_ops = {
+static struct page_ext_operations page_idle_ops __initdata = {
 	.need = need_page_idle,
 };
 #endif
 
-static struct page_ext_operations *page_ext_ops[] = {
+static struct page_ext_operations *page_ext_ops[] __initdata = {
 #ifdef CONFIG_PAGE_OWNER
 	&page_owner_ops,
 #endif
-- 
cgit v1.2.3