From 7d7ab43a33f86e39fa3ce232e84235c9ed590445 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Thu, 20 Sep 2018 11:39:39 +0200
Subject: [PATCH] BUILD: sockpair: silence a build warning at -Wextra

An invalid null-deref warning is emitted because cmsg is not checked,
though it definitely is valid given the test performed 10 lines above,
but the compiler cannot necessarily guess this. Adding a null test to
the problematic condition is enough to get rid of it and cheap enough.
---
 src/proto_sockpair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/proto_sockpair.c b/src/proto_sockpair.c
index 8f4a87462..bc8557a0d 100644
--- a/src/proto_sockpair.c
+++ b/src/proto_sockpair.c
@@ -382,7 +382,7 @@ int recv_fd_uxst(int sock)
 		return ret;
 
 	cmsg = CMSG_FIRSTHDR(&msghdr);
-	if (cmsg->cmsg_level == SOL_SOCKET &&
+	if (cmsg && cmsg->cmsg_level == SOL_SOCKET &&
 	    cmsg->cmsg_type == SCM_RIGHTS) {
 		size_t totlen = cmsg->cmsg_len -
 			CMSG_LEN(0);