[3.16.y-ckt stable] Patch "iscsi-target: Fail connection on short sendmsg writes" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    iscsi-target: Fail connection on short sendmsg writes

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 390dc51ec05c0bd26754662b72a61cc45c75cc6a Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab at linux-iscsi.org>
Date: Thu, 20 Nov 2014 20:50:07 -0800
Subject: iscsi-target: Fail connection on short sendmsg writes

commit 6bf6ca7515c1df06f5c03737537f5e0eb191e29e upstream.

This patch changes iscsit_do_tx_data() to fail on short writes
when kernel_sendmsg() returns a value different than requested
transfer length, returning -EPIPE and thus causing a connection
reset to occur.

This avoids a potential bug in the original code where a short
write would result in kernel_sendmsg() being called again with
the original iovec base + length.

In practice this has not been an issue because iscsit_do_tx_data()
is only used for transferring 48 byte headers + 4 byte digests,
along with seldom used control payloads from NOPIN + TEXT_RSP +
REJECT with less than 32k of data.

So following Al's audit of iovec consumers, go ahead and fail
the connection on short writes for now, and remove the bogus
logic ahead of his proper upstream fix.

Reported-by: Al Viro <viro at zeniv.linux.org.uk>
Cc: David S. Miller <davem at davemloft.net>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/target/iscsi/iscsi_target_util.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index fd90b28f1d94..2e96ae6cf3c1 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -1356,15 +1356,15 @@ static int iscsit_do_tx_data(
 	struct iscsi_conn *conn,
 	struct iscsi_data_count *count)
 {
-	int data = count->data_length, total_tx = 0, tx_loop = 0, iov_len;
+	int ret, iov_len;
 	struct kvec *iov_p;
 	struct msghdr msg;

 	if (!conn || !conn->sock || !conn->conn_ops)
 		return -1;

-	if (data <= 0) {
-		pr_err("Data length is: %d\n", data);
+	if (count->data_length <= 0) {
+		pr_err("Data length is: %d\n", count->data_length);
 		return -1;
 	}

@@ -1373,20 +1373,16 @@ static int iscsit_do_tx_data(
 	iov_p = count->iov;
 	iov_len = count->iov_count;

-	while (total_tx < data) {
-		tx_loop = kernel_sendmsg(conn->sock, &msg, iov_p, iov_len,
-					(data - total_tx));
-		if (tx_loop <= 0) {
-			pr_debug("tx_loop: %d total_tx %d\n",
-				tx_loop, total_tx);
-			return tx_loop;
-		}
-		total_tx += tx_loop;
-		pr_debug("tx_loop: %d, total_tx: %d, data: %d\n",
-					tx_loop, total_tx, data);
+	ret = kernel_sendmsg(conn->sock, &msg, iov_p, iov_len,
+			     count->data_length);
+	if (ret != count->data_length) {
+		pr_err("Unexpected ret: %d send data %d\n",
+		       ret, count->data_length);
+		return -EPIPE;
 	}
+	pr_debug("ret: %d, sent data: %d\n", ret, count->data_length);

-	return total_tx;
+	return ret;
 }

 int rx_data(
--
2.1.4