1 files changed, 22 insertions, 20 deletions

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 8fe165844e47..c2819a3d58a6 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -215,17 +215,12 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
 		}
 	}
 
-	if (!vma && need_mm)
-		mm = get_task_mm(alloc->tsk);
+	if (!vma && need_mm && mmget_not_zero(alloc->vma_vm_mm))
+		mm = alloc->vma_vm_mm;
 
 	if (mm) {
 		down_write(&mm->mmap_sem);
 		vma = alloc->vma;
-		if (vma && mm != alloc->vma_vm_mm) {
-			pr_err("%d: vma mm and task mm mismatch\n",
-				alloc->pid);
-			vma = NULL;
-		}
 	}
 
 	if (!vma && need_mm) {
@@ -565,7 +560,7 @@ static void binder_delete_free_buffer(struct binder_alloc *alloc,
 		binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
 				   "%d: merge free, buffer %pK do not share page with %pK or %pK\n",
 				   alloc->pid, buffer->data,
-				   prev->data, next->data);
+				   prev->data, next ? next->data : NULL);
 		binder_update_page_range(alloc, 0, buffer_start_page(buffer),
 					 buffer_start_page(buffer) + PAGE_SIZE,
 					 NULL);
@@ -720,6 +715,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
 	barrier();
 	alloc->vma = vma;
 	alloc->vma_vm_mm = vma->vm_mm;
+	mmgrab(alloc->vma_vm_mm);
 
 	return 0;
 
@@ -795,6 +791,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
 		vfree(alloc->buffer);
 	}
 	mutex_unlock(&alloc->mutex);
+	if (alloc->vma_vm_mm)
+		mmdrop(alloc->vma_vm_mm);
 
 	binder_alloc_debug(BINDER_DEBUG_OPEN_CLOSE,
 		     "%s: %d buffers %d, pages %d\n",
@@ -889,7 +887,6 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc)
 void binder_alloc_vma_close(struct binder_alloc *alloc)
 {
 	WRITE_ONCE(alloc->vma, NULL);
-	WRITE_ONCE(alloc->vma_vm_mm, NULL);
 }
 
 /**
@@ -913,6 +910,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 	struct binder_alloc *alloc;
 	uintptr_t page_addr;
 	size_t index;
+	struct vm_area_struct *vma;
 
 	alloc = page->alloc;
 	if (!mutex_trylock(&alloc->mutex))
@@ -923,16 +921,22 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 
 	index = page - alloc->pages;
 	page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;
-	if (alloc->vma) {
-		mm = get_task_mm(alloc->tsk);
-		if (!mm)
-			goto err_get_task_mm_failed;
+	vma = alloc->vma;
+	if (vma) {
+		if (!mmget_not_zero(alloc->vma_vm_mm))
+			goto err_mmget;
+		mm = alloc->vma_vm_mm;
 		if (!down_write_trylock(&mm->mmap_sem))
 			goto err_down_write_mmap_sem_failed;
+	}
+
+	list_lru_isolate(lru, item);
+	spin_unlock(lock);
 
+	if (vma) {
 		trace_binder_unmap_user_start(alloc, index);
 
-		zap_page_range(alloc->vma,
+		zap_page_range(vma,
 			       page_addr + alloc->user_buffer_offset,
 			       PAGE_SIZE);
 
@@ -950,14 +954,13 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 
 	trace_binder_unmap_kernel_end(alloc, index);
 
-	list_lru_isolate(lru, item);
-
+	spin_lock(lock);
 	mutex_unlock(&alloc->mutex);
-	return LRU_REMOVED;
+	return LRU_REMOVED_RETRY;
 
 err_down_write_mmap_sem_failed:
-	mmput(mm);
-err_get_task_mm_failed:
+	mmput_async(mm);
+err_mmget:
 err_page_already_freed:
 	mutex_unlock(&alloc->mutex);
 err_get_alloc_mutex_failed:
@@ -996,7 +999,6 @@ struct shrinker binder_shrinker = {
  */
 void binder_alloc_init(struct binder_alloc *alloc)
 {
-	alloc->tsk = current->group_leader;
 	alloc->pid = current->group_leader->pid;
 	mutex_init(&alloc->mutex);
 	INIT_LIST_HEAD(&alloc->buffers);