Re: [PATCH v2] iov_iter: don't revert iov buffer if csum error

[Ding Tianhong]

On 2017/4/29 10:46, Al Viro wrote:
> On Sat, Apr 29, 2017 at 10:38:48AM +0800, Ding Tianhong wrote:
>> The patch 327868212381 (make skb_copy_datagram_msg() et.al. preserve
>> ->msg_iter on error) will revert the iov buffer if copy to iter
>> failed, but it didn't copy any datagram if the skb_checksum_complete
>> error, so no need to revert any data at this place.
> 
> The bug is real, but I would suggest a simpler fix:
>                 if (__skb_checksum_complete(skb))
>                         return -EINVAL;
> leaving the rest as-is.
> 
Looks good, if so, we don't need the csum_error any more,

-               if (csum_fold(csum))
+
+               if (csum_fold(csum)) {
+                       iov_iter_revert(&msg->msg_iter, chunk);
+                       return -EINVAL;
+               }
+
                if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
                        netdev_rx_csum_fault(skb->dev);
        }
        return 0;
- csum_error:
-       iov_iter_revert(&msg->msg_iter, chunk);
-       return -EINVAL;
 fault:
        return -EFAULT;

DO you agree this way? :)

Thanks
Ding

> .
>