From: Vakul Garg <vakul.garg@nxp.com>
Date: Fri, 21 Dec 2018 15:16:52 +0000
Subject: tls: Do not call sk_memcopy_from_iter with zero length
Patch-mainline: v4.20
Git-commit: 65a10e28aee72903a41670170cd5330ad73c490e
References: bsc#1109837

In some conditions e.g. when tls_clone_plaintext_msg() returns -ENOSPC,
the number of bytes to be copied using subsequent function
sk_msg_memcopy_from_iter() becomes zero. This causes function
sk_msg_memcopy_from_iter() to fail which in turn causes tls_sw_sendmsg()
to return failure. To prevent it, do not call sk_msg_memcopy_from_iter()
when number of bytes to copy (indicated by 'try_to_copy') is zero.

Fixes: d829e9c4112b ("tls: convert to generic sk_msg interface")
Signed-off-by: Vakul Garg <vakul.garg@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/tls/tls_sw.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -935,10 +935,12 @@ fallback_to_reg_send:
 				    tls_ctx->tx.overhead_size);
 		}
 
-		ret = sk_msg_memcopy_from_iter(sk, &msg->msg_iter, msg_pl,
-					       try_to_copy);
-		if (ret < 0)
-			goto trim_sgl;
+		if (try_to_copy) {
+			ret = sk_msg_memcopy_from_iter(sk, &msg->msg_iter,
+						       msg_pl, try_to_copy);
+			if (ret < 0)
+				goto trim_sgl;
+		}
 
 		/* Open records defined only if successfully copied, otherwise
 		 * we would trim the sg but not reset the open record frags.