[PATCH v6 25/39] kasan, vmalloc, arm64: mark vmalloc mappings as pgprot_tagged

andrey.konovalov
2022-01-24T18:58:18Z

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@google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@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 87f8cfec50a0..7b879c77bec5 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 15e1a4fdfe0b..92e635b7490c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3108,6 +3108,15 @@ 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;