binder: fix memory leak [1/1]

PD#TV-3541

Problem:
1.only vmalloc 4KB at first.
2.if user space need more memory, try to allocate a new vmalloc
  range with large size and move all related data to new place.
3.the first 4KB is not free when release this binder.

Solution:
free the first 4KB when release binder.

Verify:
R311

Change-Id: I4429de04a260671e4626b77ec340e47e436d5c8d
Signed-off-by: changqing.gao <changqing.gao@amlogic.com>

drivers/android/binder_alloc.c

@@ -838,6 +838,9 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
 		goto err_get_vm_area_failed;
 	}
 	alloc->buffer = area->addr;
+#ifdef CONFIG_AMLOGIC_BINDER_VMALLOC
+	alloc->first_addr = area->addr;
+#endif
 	alloc->user_buffer_offset =
 		vma->vm_start - (uintptr_t)alloc->buffer;
 	mutex_unlock(&binder_alloc_mmap_lock);
@@ -958,6 +961,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
 		vfree(alloc->buffer);
 	#ifdef CONFIG_AMLOGIC_BINDER_VMALLOC
 		free_back_buffer(alloc);
+		if (alloc->first_addr && alloc->first_addr != alloc->buffer)
+			vfree(alloc->first_addr);
 	#endif
 	}
 	mutex_unlock(&alloc->mutex);

drivers/android/binder_alloc.h

@@ -113,6 +113,7 @@ struct binder_alloc {
 #ifdef CONFIG_AMLOGIC_BINDER_VMALLOC
 	size_t mapped_size;
 	void *back_buffer[MAX_BUFFER];
+	void *first_addr;
 #endif /* CONFIG_AMLOGIC_BINDER_VMALLOC */
 	ptrdiff_t user_buffer_offset;
 	struct list_head buffers;