[v8,22/40] mm/mmap: Add shadow stack pages to memory accounting

Commit Message

Rick Edgecombe March 19, 2023, 12:15 a.m. UTC

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 <[e-mail]>
Signed-off-by: Yu-cheng Yu <[e-mail]>
Signed-off-by: Rick Edgecombe <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Acked-by: Mike Rapoport (IBM) <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
Tested-by: Pengfei Xu <[e-mail]>
Tested-by: John Allen <[e-mail]>
Tested-by: Kees Cook <[e-mail]>
---
v8:
 - Update commit log verbaige (Boris)
 - Update comment around is_stack_mapping() (David Hildenbrand)

v7:
 - Change is_stack_mapping() to know about VM_SHADOW_STACK so the
   additions in vm_stat_account() can be dropped. (David Hildenbrand)

v3:
 - Remove unneeded VM_SHADOW_STACK check in accountable_mapping()
   (Kirill)

v2:
 - Remove is_shadow_stack_mapping() and just change it to directly bitwise
   and VM_SHADOW_STACK.
---
 mm/internal.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

diff --git a/mm/internal.h b/mm/internal.h
index 7920a8b7982e..2e9f313fcf67 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -491,14 +491,14 @@  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);
 }
 
 /*