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From 8daeed9570af72eb135c8ded460d2888f05b2e68 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>
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Date: Sun, 11 May 2014 22:54:58 +0200
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Subject: [PATCH 626/627] closures: Create temporary file with O_TMPFILE and
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O_CLOEXEC when available
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The open_temp_exec_file_dir function can create a temporary file without
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file system accessible link. If the O_TMPFILE flag is not defined (old
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Linux kernel or libc) the behavior is unchanged.
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The open_temp_exec_file_name function now need a new argument "flags"
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(like O_CLOEXEC) used for temporary file creation.
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The O_TMPFILE flag allow temporary file creation without race condition.
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This feature/fix prevent another process to access the (future)
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executable file from the file system.
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The O_CLOEXEC flag automatically close the temporary file for any
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execve. This avoid transmitting (executable) file descriptor to a child
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process.
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---
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src/closures.c | 29 ++++++++++++++++++++++++-----
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1 file changed, 24 insertions(+), 5 deletions(-)
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diff -rup a/src/closures.c b/src/closures.c
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--- a/src/closures.c 2019-06-14 14:24:01.510844835 -0400
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+++ b/src/closures.c 2019-06-14 14:26:48.248924350 -0400
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@@ -265,9 +265,9 @@ static size_t execsize = 0;
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/* Open a temporary file name, and immediately unlink it. */
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static int
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-open_temp_exec_file_name (char *name)
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+open_temp_exec_file_name (char *name, int flags)
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{
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- int fd = mkstemp (name);
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+ int fd = mkostemp (name, flags);
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if (fd != -1)
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unlink (name);
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@@ -280,8 +280,28 @@ static int
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open_temp_exec_file_dir (const char *dir)
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{
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static const char suffix[] = "/ffiXXXXXX";
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- size_t lendir = strlen (dir);
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- char *tempname = __builtin_alloca (lendir + sizeof (suffix));
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+ size_t lendir;
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+ int flags, fd;
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+ char *tempname;
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+
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+#ifdef O_CLOEXEC
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+ flags = O_CLOEXEC;
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+#else
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+ flags = 0;
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+#endif
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+
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+#ifdef O_TMPFILE
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+ fd = open (dir, flags | O_RDWR | O_EXCL | O_TMPFILE, 0700);
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+ /* If the running system does not support the O_TMPFILE flag then retry without it. */
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+ if (fd != -1 || (errno != EINVAL && errno != EISDIR && errno != EOPNOTSUPP)) {
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+ return fd;
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+ } else {
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+ errno = 0;
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+ }
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+#endif
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+
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+ lendir = strlen (dir);
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+ tempname = __builtin_alloca (lendir + sizeof (suffix));
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if (!tempname)
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return -1;
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@@ -289,7 +309,7 @@ open_temp_exec_file_dir (const char *dir
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memcpy (tempname, dir, lendir);
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memcpy (tempname + lendir, suffix, sizeof (suffix));
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- return open_temp_exec_file_name (tempname);
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+ return open_temp_exec_file_name (tempname, flags);
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}
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/* Open a temporary file in the directory in the named environment
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