From: Rouven Czerwinski <r.czerwinski@pengutronix.de>
Date: Thu, 6 Aug 2020 08:49:06 +0200
Subject: net/tls: allow MSG_CMSG_COMPAT in sendmsg
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Patch-mainline: v5.9-rc1
Git-commit: 1c3b63f155f637594268cd1add8335461691b314
References: bsc#1176447

Trying to use ktls on a system with 32-bit userspace and 64-bit kernel
results in a EOPNOTSUPP message during sendmsg:

  setsockopt(3, SOL_TLS, TLS_TX, …, 40) = 0
  sendmsg(3, …, msg_flags=0}, 0) = -1 EOPNOTSUPP (Operation not supported)

The tls_sw implementation does strict flag checking and does not allow
the MSG_CMSG_COMPAT flag, which is set if the message comes in through
the compat syscall.

This patch adds MSG_CMSG_COMPAT to the flag check to allow the usage of
the TLS SW implementation on systems using the compat syscall path.

Note that the same check is present in the sendmsg path for the TLS
device implementation, however the flag hasn't been added there for lack
of testing hardware.

Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/tls/tls_sw.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -935,7 +935,8 @@ int tls_sw_sendmsg(struct sock *sk, stru
 	int ret = 0;
 	int pending;
 
-	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))
+	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL |
+			       MSG_CMSG_COMPAT))
 		return -EOPNOTSUPP;
 
 	mutex_lock(&tls_ctx->tx_lock);