[PATCH v5 12/38] kmsan: x86: sync metadata pages on page fault

[glider@google.com]

KMSAN assumes shadow and origin pages for every allocated page are
accessible. For pages in vmalloc region those metadata pages reside in
[VMALLOC_END, VMALLOC_META_END), therefore we must sync a bigger memory
region.

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: linux-mm@kvack.org

---

Change-Id: I0d54855489870ef1180b37fe2120b601da464bf7
---
 arch/x86/mm/fault.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index a51df516b87bf..d22e373fa2124 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -331,11 +331,21 @@ static void dump_pagetable(unsigned long address)
 
 void vmalloc_sync_mappings(void)
 {
+#ifndef CONFIG_KMSAN
 	/*
 	 * 64-bit mappings might allocate new p4d/pud pages
 	 * that need to be propagated to all tasks' PGDs.
 	 */
 	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
+#else
+	/*
+	 * For KMSAN, make sure metadata pages for vmalloc area and modules are
+	 * also synced.
+	 */
+	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_META_END);
+	sync_global_pgds(MODULES_SHADOW_START & PGDIR_MASK,
+		MODULES_ORIGIN_END);
+#endif
 }
 
 void vmalloc_sync_unmappings(void)
@@ -360,7 +370,17 @@ static noinline int vmalloc_fault(unsigned long address)
 	pte_t *pte;
 
 	/* Make sure we are in vmalloc area: */
+#ifdef CONFIG_KMSAN
+	/*
+	 * For KMSAN, make sure metadata pages for vmalloc area and modules are
+	 * also synced.
+	 */
+	if (!(address >= VMALLOC_START && address < VMALLOC_META_END) &&
+		!(address >= MODULES_SHADOW_START &&
+		  address < MODULES_ORIGIN_END))
+#else
 	if (!(address >= VMALLOC_START && address < VMALLOC_END))
+#endif
 		return -1;
 
 	/*
-- 
2.25.1.696.g5e7596f4ac-goog