[patch 06/16] mm: Provide vm_special_mapping::close

[Thomas Gleixner]

From: Peter Zijlstra  <peterz@xxxxxxxxxxxxx>

Userspace can (malisiously) munmap() the VMAs injected into its memory
map through install_special_mapping(). In order to ensure there are no
hardware resources tied to the mapping, we need a close callback.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
---
 include/linux/mm_types.h |    3 +++
 mm/mmap.c                |    4 ++++
 2 files changed, 7 insertions(+)

--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -644,6 +644,9 @@ struct vm_special_mapping {
 
 	int (*mremap)(const struct vm_special_mapping *sm,
 		     struct vm_area_struct *new_vma);
+
+	void (*close)(const struct vm_special_mapping *sm,
+		      struct vm_area_struct *vma);
 };
 
 enum tlb_flush_reason {
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3206,6 +3206,10 @@ static int special_mapping_fault(struct
  */
 static void special_mapping_close(struct vm_area_struct *vma)
 {
+	struct vm_special_mapping *sm = vma->vm_private_data;
+
+	if (sm->close)
+		sm->close(sm, vma);
 }
 
 static const char *special_mapping_name(struct vm_area_struct *vma)