From 3e46b25376321db119bc8507ce8c8841c580e736 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>
Date: Tue, 22 Dec 2015 22:15:10 +0100
Subject: [PATCH] um: Use race-free temporary file creation
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Open the memory mapped file with the O_TMPFILE flag when available.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Acked-by: Tristan Schmelcher <tschmelcher@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
---
 arch/um/os-Linux/mem.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 840d573f7e38..8b1767668515 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -106,6 +106,17 @@ static int __init make_tempfile(const char *template)
 		}
 	}
 
+#ifdef O_TMPFILE
+	fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
+	/*
+	 * If the running system does not support O_TMPFILE flag then retry
+	 * without it.
+	 */
+	if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
+			errno != EOPNOTSUPP))
+		return fd;
+#endif
+
 	tempname = malloc(strlen(tempdir) + strlen(template) + 1);
 	if (tempname == NULL)
 		return -1;
-- 
2.20.1