Patch "Drivers: hv: fcopy: restore correct transfer length" has been added to the 4.13-stable tree

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

Drivers: hv: fcopy: restore correct transfer length

to the 4.13-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:
drivers-hv-fcopy-restore-correct-transfer-length.patch
and it can be found in the queue-4.13 subdirectory.

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

From: Olaf Hering <[email protected]>
Date: Thu, 21 Sep 2017 23:41:48 -0700
Subject: Drivers: hv: fcopy: restore correct transfer length

From: Olaf Hering <[email protected]>

commit 549e658a0919e355a2b2144dc380b3729bef7f3e upstream.

Till recently the expected length of bytes read by the daemon did depend on the context. It was either hv_start_fcopy or hv_do_fcopy. The daemon had a buffer size of two pages, which was much larger than needed.

Now the expected length of bytes read by the
daemon changed slightly. For START_FILE_COPY it is still the size of hv_start_fcopy. But for WRITE_TO_FILE and the other operations it is as large as the buffer that arrived via vmbus. In case of WRITE_TO_FILE that is slightly larger than a struct hv_do_fcopy. Since the buffer in the daemon was still larger everything was fine.

Currently, the daemon reads only what is actually needed. The new buffer layout is as large as a struct hv_do_fcopy, for the WRITE_TO_FILE operation. Since the kernel expects a slightly larger size, hvt_op_read will return -EINVAL because the daemon will read slightly less than expected. Address this by restoring the expected buffer size in case of WRITE_TO_FILE.

---
 drivers/hv/hv_fcopy.c |    4 ++++
 1 file changed, 4 insertions(+)

@@ -170,6 +170,10 @@ static void fcopy_send_data(struct work_
 		out_src = smsg_out;
 		break;
 
+	case WRITE_TO_FILE:
+		out_src = fcopy_transaction.fcopy_msg;
+		out_len = sizeof(struct hv_do_fcopy);
+		break;
 	default:
 		out_src = fcopy_transaction.fcopy_msg;
 		out_len = fcopy_transaction.recv_len;

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

queue-4.13/drivers-hv-fcopy-restore-correct-transfer-length.patch