1 files changed, 35 insertions, 8 deletions

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 3f3b7b253445..64fd96eada31 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -332,6 +332,35 @@ err_no_vma:
 	return vma ? -ENOMEM : -ESRCH;
 }
 
+
+static inline void binder_alloc_set_vma(struct binder_alloc *alloc,
+		struct vm_area_struct *vma)
+{
+	if (vma)
+		alloc->vma_vm_mm = vma->vm_mm;
+	/*
+	 * If we see alloc->vma is not NULL, buffer data structures set up
+	 * completely. Look at smp_rmb side binder_alloc_get_vma.
+	 * We also want to guarantee new alloc->vma_vm_mm is always visible
+	 * if alloc->vma is set.
+	 */
+	smp_wmb();
+	alloc->vma = vma;
+}
+
+static inline struct vm_area_struct *binder_alloc_get_vma(
+		struct binder_alloc *alloc)
+{
+	struct vm_area_struct *vma = NULL;
+
+	if (alloc->vma) {
+		/* Look at description in binder_alloc_set_vma */
+		smp_rmb();
+		vma = alloc->vma;
+	}
+	return vma;
+}
+
 static struct binder_buffer *binder_alloc_new_buf_locked(
 				struct binder_alloc *alloc,
 				size_t data_size,
@@ -348,7 +377,7 @@ static struct binder_buffer *binder_alloc_new_buf_locked(
 	size_t size, data_offsets_size;
 	int ret;
 
-	if (alloc->vma == NULL) {
+	if (!binder_alloc_get_vma(alloc)) {
 		binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
 				   "%d: binder_alloc_buf, no vma\n",
 				   alloc->pid);
@@ -723,9 +752,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
 	buffer->free = 1;
 	binder_insert_free_buffer(alloc, buffer);
 	alloc->free_async_space = alloc->buffer_size / 2;
-	barrier();
-	alloc->vma = vma;
-	alloc->vma_vm_mm = vma->vm_mm;
+	binder_alloc_set_vma(alloc, vma);
 	mmgrab(alloc->vma_vm_mm);
 
 	return 0;
@@ -754,10 +781,10 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
 	int buffers, page_count;
 	struct binder_buffer *buffer;
 
-	BUG_ON(alloc->vma);
-
 	buffers = 0;
 	mutex_lock(&alloc->mutex);
+	BUG_ON(alloc->vma);
+
 	while ((n = rb_first(&alloc->allocated_buffers))) {
 		buffer = rb_entry(n, struct binder_buffer, rb_node);
 
@@ -900,7 +927,7 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc)
  */
 void binder_alloc_vma_close(struct binder_alloc *alloc)
 {
-	WRITE_ONCE(alloc->vma, NULL);
+	binder_alloc_set_vma(alloc, NULL);
 }
 
 /**
@@ -935,7 +962,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 
 	index = page - alloc->pages;
 	page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;
-	vma = alloc->vma;
+	vma = binder_alloc_get_vma(alloc);
 	if (vma) {
 		if (!mmget_not_zero(alloc->vma_vm_mm))
 			goto err_mmget;