[PATCH mm v5 25/39] 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 v3->v4:
- Rename arch_vmalloc_pgprot_modify() to arch_vmap_pgprot_tagged()
  to be consistent with other arch vmalloc hooks.
- Move checks from arch_vmap_pgprot_tagged() to __vmalloc_node_range()
  as the same condition is used for other things in subsequent patches.

Changes v2->v3:
- Update patch description.
---
 arch/arm64/include/asm/vmalloc.h | 6 ++++++
 include/linux/vmalloc.h          | 7 +++++++
 mm/vmalloc.c                     | 9 +++++++++
 3 files changed, 22 insertions(+)

diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
index b9185503feae..38fafffe699f 100644
--- a/arch/arm64/include/asm/vmalloc.h
+++ b/arch/arm64/include/asm/vmalloc.h
@@ -25,4 +25,10 @@ static inline bool arch_vmap_pmd_supported(pgprot_t prot)
 
 #endif
 
+#define arch_vmap_pgprot_tagged arch_vmap_pgprot_tagged
+static inline pgprot_t arch_vmap_pgprot_tagged(pgprot_t prot)
+{
+	return pgprot_tagged(prot);
+}
+
 #endif /* _ASM_ARM64_VMALLOC_H */
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 34ac66a656d4..0dc02a688207 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_vmap_pgprot_tagged
+static inline pgprot_t arch_vmap_pgprot_tagged(pgprot_t prot)
+{
+	return prot;
+}
+#endif
+
 /*
  *	Highlevel APIs for driver use
  */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index da419db620ba..598bb65263c7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3107,6 +3107,15 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		goto fail;
 	}
 
+	/*
+	 * Modify protection bits to allow tagging.
+	 * This must be done before mapping by __vmalloc_area_node().
+	 */
+	if (kasan_hw_tags_enabled() &&
+	    pgprot_val(prot) == pgprot_val(PAGE_KERNEL))
+		prot = arch_vmap_pgprot_tagged(prot);
+
+	/* Allocate physical pages and map them into vmalloc space. */
 	addr = __vmalloc_area_node(area, gfp_mask, prot, shift, node);
 	if (!addr)
 		goto fail;
-- 
2.25.1