1 files changed, 43 insertions, 27 deletions

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 5649a0371a1f..9b1778c00610 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -213,7 +213,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
 
 	if (mm) {
 		mmap_read_lock(mm);
-		vma = alloc->vma;
+		vma = vma_lookup(mm, alloc->vma_addr);
 	}
 
 	if (!vma && need_mm) {
@@ -313,16 +313,21 @@ err_no_vma:
 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;
+	unsigned long vm_start = 0;
+
 	/*
-	 * 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.
+	 * Allow clearing the vma with holding just the read lock to allow
+	 * munmapping downgrade of the write lock before freeing and closing the
+	 * file using binder_alloc_vma_close().
 	 */
-	smp_wmb();
-	alloc->vma = vma;
+	if (vma) {
+		vm_start = vma->vm_start;
+		mmap_assert_write_locked(alloc->vma_vm_mm);
+	} else {
+		mmap_assert_locked(alloc->vma_vm_mm);
+	}
+
+	alloc->vma_addr = vm_start;
 }
 
 static inline struct vm_area_struct *binder_alloc_get_vma(
@@ -330,11 +335,9 @@ static inline struct vm_area_struct *binder_alloc_get_vma(
 {
 	struct vm_area_struct *vma = NULL;
 
-	if (alloc->vma) {
-		/* Look at description in binder_alloc_set_vma */
-		smp_rmb();
-		vma = alloc->vma;
-	}
+	if (alloc->vma_addr)
+		vma = vma_lookup(alloc->vma_vm_mm, alloc->vma_addr);
+
 	return vma;
 }
 
@@ -398,12 +401,15 @@ static struct binder_buffer *binder_alloc_new_buf_locked(
 	size_t size, data_offsets_size;
 	int ret;
 
+	mmap_read_lock(alloc->vma_vm_mm);
 	if (!binder_alloc_get_vma(alloc)) {
+		mmap_read_unlock(alloc->vma_vm_mm);
 		binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
 				   "%d: binder_alloc_buf, no vma\n",
 				   alloc->pid);
 		return ERR_PTR(-ESRCH);
 	}
+	mmap_read_unlock(alloc->vma_vm_mm);
 
 	data_offsets_size = ALIGN(data_size, sizeof(void *)) +
 		ALIGN(offsets_size, sizeof(void *));
@@ -788,7 +794,6 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
 	binder_insert_free_buffer(alloc, buffer);
 	alloc->free_async_space = alloc->buffer_size / 2;
 	binder_alloc_set_vma(alloc, vma);
-	mmgrab(alloc->vma_vm_mm);
 
 	return 0;
 
@@ -817,7 +822,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
 
 	buffers = 0;
 	mutex_lock(&alloc->mutex);
-	BUG_ON(alloc->vma);
+	BUG_ON(alloc->vma_addr &&
+	       vma_lookup(alloc->vma_vm_mm, alloc->vma_addr));
 
 	while ((n = rb_first(&alloc->allocated_buffers))) {
 		buffer = rb_entry(n, struct binder_buffer, rb_node);
@@ -924,17 +930,25 @@ void binder_alloc_print_pages(struct seq_file *m,
 	 * Make sure the binder_alloc is fully initialized, otherwise we might
 	 * read inconsistent state.
 	 */
-	if (binder_alloc_get_vma(alloc) != NULL) {
-		for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
-			page = &alloc->pages[i];
-			if (!page->page_ptr)
-				free++;
-			else if (list_empty(&page->lru))
-				active++;
-			else
-				lru++;
-		}
+
+	mmap_read_lock(alloc->vma_vm_mm);
+	if (binder_alloc_get_vma(alloc) == NULL) {
+		mmap_read_unlock(alloc->vma_vm_mm);
+		goto uninitialized;
 	}
+
+	mmap_read_unlock(alloc->vma_vm_mm);
+	for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
+		page = &alloc->pages[i];
+		if (!page->page_ptr)
+			free++;
+		else if (list_empty(&page->lru))
+			active++;
+		else
+			lru++;
+	}
+
+uninitialized:
 	mutex_unlock(&alloc->mutex);
 	seq_printf(m, "  pages: %d:%d:%d\n", active, lru, free);
 	seq_printf(m, "  pages high watermark: %zu\n", alloc->pages_high);
@@ -1075,6 +1089,8 @@ static struct shrinker binder_shrinker = {
 void binder_alloc_init(struct binder_alloc *alloc)
 {
 	alloc->pid = current->group_leader->pid;
+	alloc->vma_vm_mm = current->mm;
+	mmgrab(alloc->vma_vm_mm);
 	mutex_init(&alloc->mutex);
 	INIT_LIST_HEAD(&alloc->buffers);
 }
@@ -1084,7 +1100,7 @@ int binder_alloc_shrinker_init(void)
 	int ret = list_lru_init(&binder_alloc_lru);
 
 	if (ret == 0) {
-		ret = register_shrinker(&binder_shrinker);
+		ret = register_shrinker(&binder_shrinker, "android-binder");
 		if (ret)
 			list_lru_destroy(&binder_alloc_lru);
 	}