From: Andrey Konovalov <redacted>

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.

This change adds 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 <redacted>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 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 b22369f540eb..965c4bf475f1 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h

@@ -108,6 +108,13 @@ 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 7be18b292679..f37d0ed99bf9 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c

@@ -3033,6 +3033,8 @@ 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