[RFC PATCH v2 11/15] mm: Map page tables with privileged pkey

[Kevin Brodsky]

If CONFIG_KPKEYS_HARDENED_PGTABLES is enabled, map allocated page
table pages using a privileged pkey (KPKEYS_PKEY_PGTABLES), so that
page tables can only be written under guard(kpkeys_hardened_pgtables).

This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled
(default).

Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
---
 include/linux/mm.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e99040be477f..714e1af91752 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 #include <linux/cacheinfo.h>
 #include <linux/rcuwait.h>
+#include <linux/kpkeys.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -3082,6 +3083,8 @@ static inline bool __pagetable_ctor(struct ptdesc *ptdesc)
 
 	__folio_set_pgtable(folio);
 	lruvec_stat_add_folio(folio, NR_PAGETABLE);
+	if (kpkeys_protect_pgtable_memory(folio))
+		return false;
 	return true;
 }
 
@@ -3092,6 +3095,7 @@ static inline void pagetable_dtor(struct ptdesc *ptdesc)
 	ptlock_free(ptdesc);
 	__folio_clear_pgtable(folio);
 	lruvec_stat_sub_folio(folio, NR_PAGETABLE);
+	kpkeys_unprotect_pgtable_memory(folio);
 }
 
 static inline void pagetable_dtor_free(struct ptdesc *ptdesc)
-- 
2.47.0