diff --git a/Documentation/vm/index.rst b/Documentation/vm/index.rst
index 6f5ffef4b716..43bb54d897d9 100644
--- a/Documentation/vm/index.rst
+++ b/Documentation/vm/index.rst
@@ -31,6 +31,7 @@ algorithms.  If you are looking for advice on simply allocating memory, see the
    page_migration
    page_frags
    page_owner
+   page_table_check
    remap_file_pages
    slub
    split_page_table_lock
diff --git a/Documentation/vm/page_table_check.rst b/Documentation/vm/page_table_check.rst
new file mode 100644
index 000000000000..81f521ff7ea7
--- /dev/null
+++ b/Documentation/vm/page_table_check.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. _page_table_check:
+
+================
+Page Table Check
+================
+
+Introduction
+============
+
+Page table check allows to hardern the kernel by ensuring that some types of
+the memory corruptions are prevented.
+
+Page table check performs extra verifications at the time when new pages become
+accessible from the userspace by getting their page table entries (PTEs PMDs
+etc.) added into the table.
+
+In case of detected corruption, the kernel is crashed. There is a small
+performance and memory overhead associated with the page table check. Therefore,
+it is disabled by default, but can be optionally enabled on systems where the
+extra hardening outweighs the performance costs. Also, because page table check
+is synchronous, it can help with debugging double map memory corruption issues,
+by crashing kernel at the time wrong mapping occurs instead of later which is
+often the case with memory corruptions bugs.
+
+Double mapping detection logic
+==============================
+
++-------------------+-------------------+-------------------+------------------+
+| Current Mapping   | New mapping       | Permissions       | Rule             |
++===================+===================+===================+==================+
+| Anonymous         | Anonymous         | Read              | Allow            |
++-------------------+-------------------+-------------------+------------------+
+| Anonymous         | Anonymous         | Read / Write      | Prohibit         |
++-------------------+-------------------+-------------------+------------------+
+| Anonymous         | Named             | Any               | Prohibit         |
++-------------------+-------------------+-------------------+------------------+
+| Named             | Anonymous         | Any               | Prohibit         |
++-------------------+-------------------+-------------------+------------------+
+| Named             | Named             | Any               | Allow            |
++-------------------+-------------------+-------------------+------------------+
+
+Enabling Page Table Check
+=========================
+
+Build kernel with:
+
+- PAGE_TABLE_CHECK=y
+  Note, it can only be enabled on platforms where ARCH_SUPPORTS_PAGE_TABLE_CHECK
+  is available.
+
+- Boot with 'page_table_check=on' kernel parameter.
+
+Optionally, build kernel with PAGE_TABLE_CHECK_ENFORCED in order to have page
+table support without extra kernel parameter.
diff --git a/MAINTAINERS b/MAINTAINERS
index 4403b348851d..16bc8cdc1492 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14485,6 +14485,15 @@ F:	include/net/page_pool.h
 F:	include/trace/events/page_pool.h
 F:	net/core/page_pool.c
 
+PAGE TABLE CHECK
+M:	Pasha Tatashin <pasha.tatashin@soleen.com>
+M:	Andrew Morton <akpm@linux-foundation.org>
+L:	linux-mm@kvack.org
+S:	Maintained
+F:	Documentation/vm/page_table_check.rst
+F:	include/linux/page_table_check.h
+F:	mm/page_table_check.c
+
 PANASONIC LAPTOP ACPI EXTRAS DRIVER
 M:	Kenneth Chan <kenneth.t.chan@gmail.com>
 L:	platform-driver-x86@vger.kernel.org
diff --git a/arch/Kconfig b/arch/Kconfig
index 75ad877c5c48..fdba59052abc 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1307,6 +1307,9 @@ config HAVE_ARCH_PFN_VALID
 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	bool
 
+config ARCH_SUPPORTS_PAGE_TABLE_CHECK
+	bool
+
 config ARCH_SPLIT_ARG64
 	bool
 	help
diff --git a/include/linux/page_table_check.h b/include/linux/page_table_check.h
new file mode 100644
index 000000000000..38cace1da7b6
--- /dev/null
+++ b/include/linux/page_table_check.h
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2021, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+#ifndef __LINUX_PAGE_TABLE_CHECK_H
+#define __LINUX_PAGE_TABLE_CHECK_H
+
+#ifdef CONFIG_PAGE_TABLE_CHECK
+#include <linux/jump_label.h>
+
+extern struct static_key_true page_table_check_disabled;
+extern struct page_ext_operations page_table_check_ops;
+
+void __page_table_check_zero(struct page *page, unsigned int order);
+void __page_table_check_pte_clear(struct mm_struct *mm, unsigned long addr,
+				  pte_t pte);
+void __page_table_check_pmd_clear(struct mm_struct *mm, unsigned long addr,
+				  pmd_t pmd);
+void __page_table_check_pud_clear(struct mm_struct *mm, unsigned long addr,
+				  pud_t pud);
+void __page_table_check_pte_set(struct mm_struct *mm, unsigned long addr,
+				pte_t *ptep, pte_t pte);
+void __page_table_check_pmd_set(struct mm_struct *mm, unsigned long addr,
+				pmd_t *pmdp, pmd_t pmd);
+void __page_table_check_pud_set(struct mm_struct *mm, unsigned long addr,
+				pud_t *pudp, pud_t pud);
+
+static inline void page_table_check_alloc(struct page *page, unsigned int order)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_zero(page, order);
+}
+
+static inline void page_table_check_free(struct page *page, unsigned int order)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_zero(page, order);
+}
+
+static inline void page_table_check_pte_clear(struct mm_struct *mm,
+					      unsigned long addr, pte_t pte)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_pte_clear(mm, addr, pte);
+}
+
+static inline void page_table_check_pmd_clear(struct mm_struct *mm,
+					      unsigned long addr, pmd_t pmd)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_pmd_clear(mm, addr, pmd);
+}
+
+static inline void page_table_check_pud_clear(struct mm_struct *mm,
+					      unsigned long addr, pud_t pud)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_pud_clear(mm, addr, pud);
+}
+
+static inline void page_table_check_pte_set(struct mm_struct *mm,
+					    unsigned long addr, pte_t *ptep,
+					    pte_t pte)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_pte_set(mm, addr, ptep, pte);
+}
+
+static inline void page_table_check_pmd_set(struct mm_struct *mm,
+					    unsigned long addr, pmd_t *pmdp,
+					    pmd_t pmd)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_pmd_set(mm, addr, pmdp, pmd);
+}
+
+static inline void page_table_check_pud_set(struct mm_struct *mm,
+					    unsigned long addr, pud_t *pudp,
+					    pud_t pud)
+{
+	if (static_branch_likely(&page_table_check_disabled))
+		return;
+
+	__page_table_check_pud_set(mm, addr, pudp, pud);
+}
+
+#else
+
+static inline void page_table_check_alloc(struct page *page, unsigned int order)
+{
+}
+
+static inline void page_table_check_free(struct page *page, unsigned int order)
+{
+}
+
+static inline void page_table_check_pte_clear(struct mm_struct *mm,
+					      unsigned long addr, pte_t pte)
+{
+}
+
+static inline void page_table_check_pmd_clear(struct mm_struct *mm,
+					      unsigned long addr, pmd_t pmd)
+{
+}
+
+static inline void page_table_check_pud_clear(struct mm_struct *mm,
+					      unsigned long addr, pud_t pud)
+{
+}
+
+static inline void page_table_check_pte_set(struct mm_struct *mm,
+					    unsigned long addr, pte_t *ptep,
+					    pte_t pte)
+{
+}
+
+static inline void page_table_check_pmd_set(struct mm_struct *mm,
+					    unsigned long addr, pmd_t *pmdp,
+					    pmd_t pmd)
+{
+}
+
+static inline void page_table_check_pud_set(struct mm_struct *mm,
+					    unsigned long addr, pud_t *pudp,
+					    pud_t pud)
+{
+}
+
+#endif /* CONFIG_PAGE_TABLE_CHECK */
+#endif /* __LINUX_PAGE_TABLE_CHECK_H */
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 1e73717802f8..5bd5bb097252 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -62,6 +62,30 @@ config PAGE_OWNER
 
 	  If unsure, say N.
 
+config PAGE_TABLE_CHECK
+	bool "Check for invalid mappings in user page tables"
+	depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
+	select PAGE_EXTENSION
+	help
+	  Check that anonymous page is not being mapped twice with read write
+	  permissions. Check that anonymous and file pages are not being
+	  erroneously shared. Since the checking is performed at the time
+	  entries are added and removed to user page tables, leaking, corruption
+	  and double mapping problems are detected synchronously.
+
+	  If unsure say "n".
+
+config PAGE_TABLE_CHECK_ENFORCED
+	bool "Enforce the page table checking by default"
+	depends on PAGE_TABLE_CHECK
+	help
+	  Always enable page table checking.  By default the page table checking
+	  is disabled, and can be optionally enabled via page_table_check=on
+	  kernel parameter. This config enforces that page table check is always
+	  enabled.
+
+	  If unsure say "n".
+
 config PAGE_POISONING
 	bool "Poison pages after freeing"
 	help
diff --git a/mm/Makefile b/mm/Makefile
index 7919cd7f13f2..588d3113f3b0 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
 obj-$(CONFIG_CMA)	+= cma.o
 obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
+obj-$(CONFIG_PAGE_TABLE_CHECK) += page_table_check.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
 obj-$(CONFIG_SECRETMEM) += secretmem.o
 obj-$(CONFIG_CMA_SYSFS) += cma_sysfs.o
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 77253ea6031e..edfd6c81af82 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -64,6 +64,7 @@
 #include <linux/sched/rt.h>
 #include <linux/sched/mm.h>
 #include <linux/page_owner.h>
+#include <linux/page_table_check.h>
 #include <linux/kthread.h>
 #include <linux/memcontrol.h>
 #include <linux/ftrace.h>
@@ -1308,6 +1309,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
 		if (memcg_kmem_enabled() && PageMemcgKmem(page))
 			__memcg_kmem_uncharge_page(page, order);
 		reset_page_owner(page, order);
+		page_table_check_free(page, order);
 		return false;
 	}
 
@@ -1347,6 +1349,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
 	page_cpupid_reset_last(page);
 	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
 	reset_page_owner(page, order);
+	page_table_check_free(page, order);
 
 	if (!PageHighMem(page)) {
 		debug_check_no_locks_freed(page_address(page),
@@ -2421,6 +2424,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 	}
 
 	set_page_owner(page, order, gfp_flags);
+	page_table_check_alloc(page, order);
 }
 
 static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
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);
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
new file mode 100644
index 000000000000..7504e7caa2a1
--- /dev/null
+++ b/mm/page_table_check.c
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2021, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+#include <linux/mm.h>
+#include <linux/page_table_check.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)	"page_table_check: " fmt
+
+struct page_table_check {
+	atomic_t anon_map_count;
+	atomic_t file_map_count;
+};
+
+static bool __page_table_check_enabled __initdata =
+				IS_ENABLED(CONFIG_PAGE_TABLE_CHECK_ENFORCED);
+
+DEFINE_STATIC_KEY_TRUE(page_table_check_disabled);
+EXPORT_SYMBOL(page_table_check_disabled);
+
+static int __init early_page_table_check_param(char *buf)
+{
+	if (!buf)
+		return -EINVAL;
+
+	if (strcmp(buf, "on") == 0)
+		__page_table_check_enabled = true;
+	else if (strcmp(buf, "off") == 0)
+		__page_table_check_enabled = false;
+
+	return 0;
+}
+
+early_param("page_table_check", early_page_table_check_param);
+
+static bool __init need_page_table_check(void)
+{
+	return __page_table_check_enabled;
+}
+
+static void __init init_page_table_check(void)
+{
+	if (!__page_table_check_enabled)
+		return;
+	static_branch_disable(&page_table_check_disabled);
+}
+
+struct page_ext_operations page_table_check_ops = {
+	.size = sizeof(struct page_table_check),
+	.need = need_page_table_check,
+	.init = init_page_table_check,
+};
+
+static struct page_table_check *get_page_table_check(struct page_ext *page_ext)
+{
+	BUG_ON(!page_ext);
+	return (void *)(page_ext) + page_table_check_ops.offset;
+}
+
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+	return (pte_val(pte) & _PAGE_PRESENT) && (pte_val(pte) & _PAGE_USER);
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+	return pmd_leaf(pmd) && (pmd_val(pmd) & _PAGE_PRESENT) &&
+		(pmd_val(pmd) & _PAGE_USER);
+}
+
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+	return pud_leaf(pud) && (pud_val(pud) & _PAGE_PRESENT) &&
+		(pud_val(pud) & _PAGE_USER);
+}
+
+/*
+ * An enty is removed from the page table, decrement the counters for that page
+ * verify that it is of correct type and counters do not become negative.
+ */
+static void page_table_check_clear(struct mm_struct *mm, unsigned long addr,
+				   unsigned long pfn, unsigned long pgcnt)
+{
+	struct page_ext *page_ext;
+	struct page *page;
+	bool anon;
+	int i;
+
+	if (!pfn_valid(pfn))
+		return;
+
+	page = pfn_to_page(pfn);
+	page_ext = lookup_page_ext(page);
+	anon = PageAnon(page);
+
+	for (i = 0; i < pgcnt; i++) {
+		struct page_table_check *ptc = get_page_table_check(page_ext);
+
+		if (anon) {
+			BUG_ON(atomic_read(&ptc->file_map_count));
+			BUG_ON(atomic_dec_return(&ptc->anon_map_count) < 0);
+		} else {
+			BUG_ON(atomic_read(&ptc->anon_map_count));
+			BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0);
+		}
+		page_ext = page_ext_next(page_ext);
+	}
+}
+
+/*
+ * A new enty is added to the page table, increment the counters for that page
+ * verify that it is of correct type and is not being mapped with a different
+ * type to a different process.
+ */
+static void page_table_check_set(struct mm_struct *mm, unsigned long addr,
+				 unsigned long pfn, unsigned long pgcnt,
+				 bool rw)
+{
+	struct page_ext *page_ext;
+	struct page *page;
+	bool anon;
+	int i;
+
+	if (!pfn_valid(pfn))
+		return;
+
+	page = pfn_to_page(pfn);
+	page_ext = lookup_page_ext(page);
+	anon = PageAnon(page);
+
+	for (i = 0; i < pgcnt; i++) {
+		struct page_table_check *ptc = get_page_table_check(page_ext);
+
+		if (anon) {
+			BUG_ON(atomic_read(&ptc->file_map_count));
+			BUG_ON(atomic_inc_return(&ptc->anon_map_count) > 1 && rw);
+		} else {
+			BUG_ON(atomic_read(&ptc->anon_map_count));
+			BUG_ON(atomic_inc_return(&ptc->file_map_count) < 0);
+		}
+		page_ext = page_ext_next(page_ext);
+	}
+}
+
+/*
+ * page is on free list, or is being allocated, verify that counters are zeroes
+ * crash if they are not.
+ */
+void __page_table_check_zero(struct page *page, unsigned int order)
+{
+	struct page_ext *page_ext = lookup_page_ext(page);
+	int i;
+
+	BUG_ON(!page_ext);
+	for (i = 0; i < (1 << order); i++) {
+		struct page_table_check *ptc = get_page_table_check(page_ext);
+
+		BUG_ON(atomic_read(&ptc->anon_map_count));
+		BUG_ON(atomic_read(&ptc->file_map_count));
+		page_ext = page_ext_next(page_ext);
+	}
+}
+
+void __page_table_check_pte_clear(struct mm_struct *mm, unsigned long addr,
+				  pte_t pte)
+{
+	if (&init_mm == mm)
+		return;
+
+	if (pte_user_accessible_page(pte)) {
+		page_table_check_clear(mm, addr, pte_pfn(pte),
+				       PAGE_SIZE >> PAGE_SHIFT);
+	}
+}
+EXPORT_SYMBOL(__page_table_check_pte_clear);
+
+void __page_table_check_pmd_clear(struct mm_struct *mm, unsigned long addr,
+				  pmd_t pmd)
+{
+	if (&init_mm == mm)
+		return;
+
+	if (pmd_user_accessible_page(pmd)) {
+		page_table_check_clear(mm, addr, pmd_pfn(pmd),
+				       PMD_PAGE_SIZE >> PAGE_SHIFT);
+	}
+}
+EXPORT_SYMBOL(__page_table_check_pmd_clear);
+
+void __page_table_check_pud_clear(struct mm_struct *mm, unsigned long addr,
+				  pud_t pud)
+{
+	if (&init_mm == mm)
+		return;
+
+	if (pud_user_accessible_page(pud)) {
+		page_table_check_clear(mm, addr, pud_pfn(pud),
+				       PUD_PAGE_SIZE >> PAGE_SHIFT);
+	}
+}
+EXPORT_SYMBOL(__page_table_check_pud_clear);
+
+void __page_table_check_pte_set(struct mm_struct *mm, unsigned long addr,
+				pte_t *ptep, pte_t pte)
+{
+	pte_t old_pte;
+
+	if (&init_mm == mm)
+		return;
+
+	old_pte = *ptep;
+	if (pte_user_accessible_page(old_pte)) {
+		page_table_check_clear(mm, addr, pte_pfn(old_pte),
+				       PAGE_SIZE >> PAGE_SHIFT);
+	}
+
+	if (pte_user_accessible_page(pte)) {
+		page_table_check_set(mm, addr, pte_pfn(pte),
+				     PAGE_SIZE >> PAGE_SHIFT,
+				     pte_write(pte));
+	}
+}
+EXPORT_SYMBOL(__page_table_check_pte_set);
+
+void __page_table_check_pmd_set(struct mm_struct *mm, unsigned long addr,
+				pmd_t *pmdp, pmd_t pmd)
+{
+	pmd_t old_pmd;
+
+	if (&init_mm == mm)
+		return;
+
+	old_pmd = *pmdp;
+	if (pmd_user_accessible_page(old_pmd)) {
+		page_table_check_clear(mm, addr, pmd_pfn(old_pmd),
+				       PMD_PAGE_SIZE >> PAGE_SHIFT);
+	}
+
+	if (pmd_user_accessible_page(pmd)) {
+		page_table_check_set(mm, addr, pmd_pfn(pmd),
+				     PMD_PAGE_SIZE >> PAGE_SHIFT,
+				     pmd_write(pmd));
+	}
+}
+EXPORT_SYMBOL(__page_table_check_pmd_set);
+
+void __page_table_check_pud_set(struct mm_struct *mm, unsigned long addr,
+				pud_t *pudp, pud_t pud)
+{
+	pud_t old_pud;
+
+	if (&init_mm == mm)
+		return;
+
+	old_pud = *pudp;
+	if (pud_user_accessible_page(old_pud)) {
+		page_table_check_clear(mm, addr, pud_pfn(old_pud),
+				       PUD_PAGE_SIZE >> PAGE_SHIFT);
+	}
+
+	if (pud_user_accessible_page(pud)) {
+		page_table_check_set(mm, addr, pud_pfn(pud),
+				     PUD_PAGE_SIZE >> PAGE_SHIFT,
+				     pud_write(pud));
+	}
+}
+EXPORT_SYMBOL(__page_table_check_pud_set);
