[tip: x86/shstk] mm/mmap: Add shadow stack pages to memory accounting

[tip-bot2 for Rick Edgecombe]

The following commit has been merged into the x86/shstk branch of tip:

Commit-ID:     6538963ccabd17c61265a8fb497c76727f6bc638
Gitweb:        https://git.kernel.org/tip/6538963ccabd17c61265a8fb497c76727f6bc638
Author:        Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
AuthorDate:    Mon, 12 Jun 2023 17:10:45 -07:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 15 Jun 2023 16:31:33 -07:00

mm/mmap: Add shadow stack pages to memory accounting

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
properly.

Co-developed-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
Tested-by: John Allen <john.allen@xxxxxxx>
Tested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20230613001108.3040476-20-rick.p.edgecombe%40intel.com
---
 mm/internal.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 68410c6..dd2ded3 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -535,14 +535,14 @@ static inline bool is_exec_mapping(vm_flags_t flags)
 }
 
 /*
- * Stack area - automatically grows in one direction
+ * Stack area (including shadow stacks)
  *
  * VM_GROWSUP / VM_GROWSDOWN VMAs are always private anonymous:
  * do_mmap() forbids all other combinations.
  */
 static inline bool is_stack_mapping(vm_flags_t flags)
 {
-	return (flags & VM_STACK) == VM_STACK;
+	return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK);
 }
 
 /*