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From 8daeed9570af72eb135c8ded460d2888f05b2e68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>
Date: Sun, 11 May 2014 22:54:58 +0200
Subject: [PATCH 626/627] closures: Create temporary file with O_TMPFILE and
O_CLOEXEC when available
The open_temp_exec_file_dir function can create a temporary file without
file system accessible link. If the O_TMPFILE flag is not defined (old
Linux kernel or libc) the behavior is unchanged.
The open_temp_exec_file_name function now need a new argument "flags"
(like O_CLOEXEC) used for temporary file creation.
The O_TMPFILE flag allow temporary file creation without race condition.
This feature/fix prevent another process to access the (future)
executable file from the file system.
The O_CLOEXEC flag automatically close the temporary file for any
execve. This avoid transmitting (executable) file descriptor to a child
process.
---
src/closures.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
diff --git a/src/closures.c b/src/closures.c
index c7863f3..9799ce6 100644
--- a/src/closures.c
+++ b/src/closures.c
@@ -265,9 +265,9 @@ static size_t execsize = 0;
/* Open a temporary file name, and immediately unlink it. */
static int
-open_temp_exec_file_name (char *name)
+open_temp_exec_file_name (char *name, int flags)
{
- int fd = mkstemp (name);
+ int fd = mkostemp (name, flags);
if (fd != -1)
unlink (name);
@@ -280,8 +280,27 @@ static int
open_temp_exec_file_dir (const char *dir)
{
static const char suffix[] = "/ffiXXXXXX";
- int lendir = strlen (dir);
- char *tempname = __builtin_alloca (lendir + sizeof (suffix));
+ int lendir, flags, fd;
+ char *tempname;
+
+#ifdef O_CLOEXEC
+ flags = O_CLOEXEC;
+#else
+ flags = 0;
+#endif
+
+#ifdef O_TMPFILE
+ fd = open (dir, flags | O_RDWR | O_EXCL | O_TMPFILE, 0700);
+ /* If the running system does not support the O_TMPFILE flag then retry without it. */
+ if (fd != -1 || (errno != EINVAL && errno != EISDIR && errno != EOPNOTSUPP)) {
+ return fd;
+ } else {
+ errno = 0;
+ }
+#endif
+
+ lendir = strlen (dir);
+ tempname = __builtin_alloca (lendir + sizeof (suffix));
if (!tempname)
return -1;
@@ -289,7 +308,7 @@ open_temp_exec_file_dir (const char *dir)
memcpy (tempname, dir, lendir);
memcpy (tempname + lendir, suffix, sizeof (suffix));
- return open_temp_exec_file_name (tempname);
+ return open_temp_exec_file_name (tempname, flags);
}
/* Open a temporary file in the directory in the named environment
--
1.7.12.1