Patch "iov_iter: don't revert iov buffer if csum error" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

iov_iter: don't revert iov buffer if csum error

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iov_iter-don-t-revert-iov-buffer-if-csum-error.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ding Tianhong <[email protected]>
Date: Sat, 29 Apr 2017 10:38:48 +0800
Subject: iov_iter: don't revert iov buffer if csum error

From: Ding Tianhong <[email protected]>

commit a6a5993243550b09f620941dea741b7421fdf79c upstream.

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.

v2: Sabrina notice that return -EFAULT when checksum error is not correct
here, it would confuse the caller about the return value, so fix it.

---
 net/core/datagram.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

@@ -740,7 +740,7 @@ int skb_copy_and_csum_datagram_msg(struc
 
 	if (msg_data_left(msg) < chunk) {
 		if (__skb_checksum_complete(skb))
-			goto csum_error;
+			return -EINVAL;
 		if (skb_copy_datagram_msg(skb, hlen, msg, chunk))
 			goto fault;
 	} else {

@@ -748,15 +748,16 @@ int skb_copy_and_csum_datagram_msg(struc
 		if (skb_copy_and_csum_datagram(skb, hlen, &msg->msg_iter,
 					       chunk, &csum))
 			goto fault;
-		if (csum_fold(csum))
-			goto csum_error;
+
+		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;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/iov_iter-don-t-revert-iov-buffer-if-csum-error.patch