linux-kernel - [PATCH v3 2/2] um: Use race-free temporary file creation

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Message-Id: <1449706184-19284-3-git-send-email-mic@digikod.net>
Date:	Thu, 10 Dec 2015 01:09:44 +0100
From:	Mickaël Salaün <mic@...ikod.net>
To:	linux-kernel@...r.kernel.org
Cc:	Mickaël Salaün <mic@...ikod.net>,
	Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	Tristan Schmelcher <tschmelcher@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	user-mode-linux-devel@...ts.sourceforge.net,
	user-mode-linux-user@...ts.sourceforge.net
Subject: [PATCH v3 2/2] um: Use race-free temporary file creation

Open the memory mapped file with the O_TMPFILE flag when available.

Signed-off-by: Mickaël Salaün <mic@...ikod.net>
Cc: Jeff Dike <jdike@...toit.com>
Cc: Richard Weinberger <richard@....at>
Acked-by: Tristan Schmelcher <tschmelcher@...gle.com>
---
 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 840d573..8b17676 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;
-- 
2.6.2

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