[PATCH mm v3 25/38] kasan, vmalloc, arm64: mark vmalloc mappings as pgprot_tagged

[andrey.konovalov at linux.dev]

From: Andrey Konovalov <andreyknvl at google.com>

HW_TAGS KASAN relies on ARM Memory Tagging Extension (MTE). With MTE,
a memory region must be mapped as MT_NORMAL_TAGGED to allow setting
memory tags via MTE-specific instructions.

Add proper protection bits to vmalloc() allocations. These allocations
are always backed by page_alloc pages, so the tags will actually be
getting set on the corresponding physical memory.

Signed-off-by: Andrey Konovalov <andreyknvl at google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>

---

Changes v2->v3:
- Update patch description.
---
 arch/arm64/include/asm/vmalloc.h | 10 ++++++++++
 include/linux/vmalloc.h          |  7 +++++++
 mm/vmalloc.c                     |  2 ++
 3 files changed, 19 insertions(+)

diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
index b9185503feae..3d35adf365bf 100644
--- a/arch/arm64/include/asm/vmalloc.h
+++ b/arch/arm64/include/asm/vmalloc.h
@@ -25,4 +25,14 @@ static inline bool arch_vmap_pmd_supported(pgprot_t prot)
 
 #endif
 
+#define arch_vmalloc_pgprot_modify arch_vmalloc_pgprot_modify
+static inline pgprot_t arch_vmalloc_pgprot_modify(pgprot_t prot)
+{
+	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS) &&
+			(pgprot_val(prot) == pgprot_val(PAGE_KERNEL)))
+		prot = pgprot_tagged(prot);
+
+	return prot;
+}
+
 #endif /* _ASM_ARM64_VMALLOC_H */
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 28becb10d013..760caeedd749 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -115,6 +115,13 @@ static inline int arch_vmap_pte_supported_shift(unsigned long size)
 }
 #endif
 
+#ifndef arch_vmalloc_pgprot_modify
+static inline pgprot_t arch_vmalloc_pgprot_modify(pgprot_t prot)
+{
+	return prot;
+}
+#endif
+
 /*
  *	Highlevel APIs for driver use
  */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 837ed355bfc6..58bd2f7f86d7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3060,6 +3060,8 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		return NULL;
 	}
 
+	prot = arch_vmalloc_pgprot_modify(prot);
+
 	if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP)) {
 		unsigned long size_per_node;
 
-- 
2.25.1