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=== Description (from pull-request) ===
lxc_make_tmpfile() uses mkstemp() internally, and thus expects the
template to contain 'XXXXXX' and be writable.

The existing code in make_anonymous_mount_file() did not work in
case the memfd_create() syscall was not available.

Furthermore, mkstemp() modifies its template argument, hence it
should not be a constant, or undefined behavior can happen. Fixed
both occurrences.
From 146560a916ba941eb514d43e246bb9f5b0026899 Mon Sep 17 00:00:00 2001
From: Thomas Moschny <thomas.mosc...@gmx.de>
Date: Fri, 6 Apr 2018 10:08:18 +0200
Subject: [PATCH] Fix temp file creation.

lxc_make_tmpfile() uses mkstemp() internally, and thus expects the
template to contain 'XXXXXX' and be writable.

Signed-off-by: Thomas Moschny <thomas.mosc...@gmx.de>
---
 src/lxc/conf.c    | 4 +++-
 src/lxc/ringbuf.c | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 745584308..8ddaaaa29 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -2288,7 +2288,9 @@ FILE *make_anonymous_mount_file(struct lxc_list *mount)
        if (fd < 0) {
                if (errno != ENOSYS)
                        return NULL;
-               fd = lxc_make_tmpfile((char *){P_tmpdir "/.lxc_mount_file"}, 
true);
+
+               char template[] = P_tmpdir "/.lxc_mount_file_XXXXXX";
+               fd = lxc_make_tmpfile(template, true);
                if (fd < 0) {
                        SYSERROR("Could not create temporary mount file");
                        return NULL;
diff --git a/src/lxc/ringbuf.c b/src/lxc/ringbuf.c
index 1299fe709..a1b21112a 100644
--- a/src/lxc/ringbuf.c
+++ b/src/lxc/ringbuf.c
@@ -55,7 +55,8 @@ int lxc_ringbuf_create(struct lxc_ringbuf *buf, size_t size)
                if (errno != ENOSYS)
                        goto on_error;
 
-               memfd = lxc_make_tmpfile((char 
*){P_tmpdir"/.lxc_ringbuf_XXXXXX"}, true);
+               char template[] = P_tmpdir "/.lxc_ringbuf_XXXXXX";
+               memfd = lxc_make_tmpfile(template, true);
        }
        if (memfd < 0)
                goto on_error;
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