Re: [PATCH v3 3/3] kasan: arm64: Fix pcpu_page_first_chunk crash with KASAN_VMALLOC

On Mon, 9 Aug 2021 at 13:10, Kefeng Wang [off-list ref] wrote:

On 2021/8/9 17:37, Kefeng Wang wrote:

quoted

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.

Should add Acked-by: Marco Elver [off-list ref] [for KASAN parts] ,

My Ack is still valid, thanks for noting.

quoted

Signed-off-by: Kefeng Wang <redacted>
---
  arch/arm64/mm/kasan_init.c | 16 ++++++++++++++++
  include/linux/kasan.h      |  6 ++++++
  mm/kasan/init.c            |  5 +++++
  mm/vmalloc.c               |  1 +
  4 files changed, 28 insertions(+)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 61b52a92b8b6..5b996ca4d996 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c

@@ -287,6 +287,22 @@ 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, NUMA_NO_NODE);
+}
+#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 1e8fe08725b8..66a7e1ea2561 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c

@@ -2253,6 +2253,7 @@ 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)

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