Hi,
On 2020/2/25 16:33, zhangfei wrote:
Hi, Zaibo
On 2020/2/24 下午3:17, Xu Zaibo wrote:
@@ -585,6 +595,13 @@ void uacce_remove(struct uacce_device *uacce)
cdev_device_del(uacce->cdev, &uacce->dev);
xa_erase(&uacce_xa, uacce->dev_id);
put_device(&uacce->dev);
+
+ /*
+ * unmap remainning mapping from user space, preventing user still
+ * access the mmaped area while parent device is already removed
+ */
+ if (uacce->inode)
+ unmap_mapping_range(uacce->inode->i_mapping, 0, 0, 1);
Should we unmap them at the first of 'uacce_remove', and before
'uacce_put_queue'?
We can do this,
Though it does not matter, since user space can not interrupt kernel
function uacce_remove.
I think it matters :)
Image that the process holds the uacce queue is running(read and write
the queue), then you do 'uacce_remove'.
The process is running(read and write the queue) well in the time
between 'uacce_put_queue' and
'unmap_mapping_range', however, the queue with its DMA memory may be
gotten and used by
other guys in this time, since you have released them in kernel. As a
result, the running process will be a disaster.
cheers,
Zaibo
.
Thanks
.
