[PATCH v2 3/3] kasan: arm64: Fix pcpu_page_first_chunk crash with KASAN_VMALLOC

[Kefeng Wang]

With KASAN_VMALLOC and NEED_PER_CPU_PAGE_FIRST_CHUNK, it crashs,

Unable to handle kernel paging request at virtual address ffff7000028f2000
...
swapper pgtable: 64k pages, 48-bit VAs, pgdp=0000000042440000
[ffff7000028f2000] pgd=000000063e7c0003, p4d=000000063e7c0003, pud=000000063e7c0003, pmd=000000063e7b0003, pte=0000000000000000
Internal error: Oops: 96000007 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.0-rc4-00003-gc6e6e28f3f30-dirty #62
Hardware name: linux,dummy-virt (DT)
pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO BTYPE=--)
pc : kasan_check_range+0x90/0x1a0
lr : memcpy+0x88/0xf4
sp : ffff80001378fe20
...
Call trace:
 kasan_check_range+0x90/0x1a0
 pcpu_page_first_chunk+0x3f0/0x568
 setup_per_cpu_areas+0xb8/0x184
 start_kernel+0x8c/0x328

The vm area used in vm_area_register_early() has no kasan shadow memory,
Let's add a new kasan_populate_early_vm_area_shadow() function to populate
the vm area shadow memory to fix the issue.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 arch/arm64/mm/kasan_init.c | 17 +++++++++++++++++
 include/linux/kasan.h      |  6 ++++++
 mm/kasan/init.c            |  5 +++++
 mm/vmalloc.c               |  1 +
 4 files changed, 29 insertions(+)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 61b52a92b8b6..46c1b3722901 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -287,6 +287,23 @@ static void __init kasan_init_depth(void)
 	init_task.kasan_depth = 0;
 }
 
+#ifdef CONFIG_KASAN_VMALLOC
+void __init kasan_populate_early_vm_area_shadow(void *start, unsigned long size)
+{
+	unsigned long shadow_start, shadow_end;
+
+	if (!is_vmalloc_or_module_addr(start))
+		return;
+
+	shadow_start = (unsigned long)kasan_mem_to_shadow(start);
+	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
+	shadow_end = (unsigned long)kasan_mem_to_shadow(start + size);
+	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
+	kasan_map_populate(shadow_start, shadow_end,
+			   early_pfn_to_nid(virt_to_pfn(start)));
+}
+#endif
+
 void __init kasan_init(void)
 {
 	kasan_init_shadow();
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index dd874a1ee862..3f8c26d9ef82 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -133,6 +133,8 @@ struct kasan_cache {
 	bool is_kmalloc;
 };
 
+void kasan_populate_early_vm_area_shadow(void *start, unsigned long size);
+
 slab_flags_t __kasan_never_merge(void);
 static __always_inline slab_flags_t kasan_never_merge(void)
 {
@@ -303,6 +305,10 @@ void kasan_restore_multi_shot(bool enabled);
 
 #else /* CONFIG_KASAN */
 
+static inline void kasan_populate_early_vm_area_shadow(void *start,
+						       unsigned long size)
+{ }
+
 static inline slab_flags_t kasan_never_merge(void)
 {
 	return 0;
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index cc64ed6858c6..d39577d088a1 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -279,6 +279,11 @@ int __ref kasan_populate_early_shadow(const void *shadow_start,
 	return 0;
 }
 
+void __init __weak kasan_populate_early_vm_area_shadow(void *start,
+						       unsigned long size)
+{
+}
+
 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
 {
 	pte_t *pte;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a98cf97f032f..f19e07314ee5 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2249,6 +2249,7 @@ void __init vm_area_register_early(struct vm_struct *vm, size_t align)
 	vm->addr = (void *)addr;
 
 	vm_area_add_early(vm);
+	kasan_populate_early_vm_area_shadow(vm->addr, vm->size);
 }
 
 static void vmap_init_free_space(void)
-- 
2.26.2