Re: [PATCH v6 22/41] mm/mmap: Add shadow stack pages to memory accounting

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On 18.02.23 22:14, Rick Edgecombe wrote:
From: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>

The x86 Control-flow Enforcement Technology (CET) feature includes a new
type of memory called shadow stack. This shadow stack memory has some
unusual properties, which requires some core mm changes to function

Account shadow stack pages to stack memory.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
Tested-by: John Allen <john.allen@xxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Co-developed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>

  - Remove unneeded VM_SHADOW_STACK check in accountable_mapping()

  - Remove is_shadow_stack_mapping() and just change it to directly bitwise

Yu-cheng v26:
  - Remove redundant #ifdef CONFIG_MMU.

Yu-cheng v25:
  - Remove #ifdef CONFIG_ARCH_HAS_SHADOW_STACK for is_shadow_stack_mapping().
  mm/mmap.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 425a9349e610..9f85596cce31 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3290,6 +3290,8 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
  		mm->exec_vm += npages;
  	else if (is_stack_mapping(flags))
  		mm->stack_vm += npages;
+	else if (flags & VM_SHADOW_STACK)
+		mm->stack_vm += npages;

Why not modify is_stack_mapping() ?


David / dhildenb

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