[PATCH 6/8] binder: remove cached alloc->vma pointer

[Carlos Llamas <cmllamas@google.com>]

All usage of the alloc->vma pointer has been removed from binder.
Instead, paths has been refactored to use either vma_lookup() or the
alloc->mapped state. Using the alloc->vma was unsafe and required the
mmap_sem in exclusive mode, which caused several performance and
security issues in the past.

Cc: Minchan Kim <minchan@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
---
 drivers/android/binder_alloc.c | 14 --------------
 drivers/android/binder_alloc.h |  3 ---
 2 files changed, 17 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index aa299cbdab92..a4b7bf8696dd 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -369,20 +369,6 @@ static void binder_lru_freelist_del(struct binder_alloc *alloc,
 	}
 }
 
-static inline void binder_alloc_set_vma(struct binder_alloc *alloc,
-		struct vm_area_struct *vma)
-{
-	/* pairs with smp_load_acquire in binder_alloc_get_vma() */
-	smp_store_release(&alloc->vma, vma);
-}
-
-static inline struct vm_area_struct *binder_alloc_get_vma(
-		struct binder_alloc *alloc)
-{
-	/* pairs with smp_store_release in binder_alloc_set_vma() */
-	return smp_load_acquire(&alloc->vma);
-}
-
 static void debug_no_space_locked(struct binder_alloc *alloc)
 {
 	size_t largest_alloc_size = 0;
diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index 89f6fa25c670..b9e2e9dc90b3 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -61,8 +61,6 @@ struct binder_buffer {
 /**
  * struct binder_alloc - per-binder proc state for binder allocator
  * @mutex:              protects binder_alloc fields
- * @vma:                vm_area_struct passed to mmap_handler
- *                      (invariant after mmap)
  * @mm:                 copy of task->mm (invariant after open)
  * @buffer:             base of per-proc address space mapped via mmap
  * @buffers:            list of all buffers for this proc
@@ -86,7 +84,6 @@ struct binder_buffer {
  */
 struct binder_alloc {
 	struct mutex mutex;
-	struct vm_area_struct *vma;
 	struct mm_struct *mm;
 	unsigned long buffer;
 	struct list_head buffers;
-- 
2.47.0.199.ga7371fff76-goog