[...]
 
+/*
+ * Creates a new temporary file and returns an fd to it. The file has no name
+ * (see open(2) regarding O_TMPFILE) and is deleted when the fd is closed.
+ */
+static inline int tmpfd(void)
+{
+	int fd;
+
+	fd = syscall(__NR_openat, 0, "/", O_TMPFILE | O_RDWR, 0666);
+	ASSERT_GE(fd, 0);

The man pages [1] discuss using O_EXCL with O_TMPFILE to prevent fd from being linked into the filesystem with linkat [2]; is this something worth considering here if we want to discourage files opened with tmpfd() from being linked at any time? Just curious, I imagine it isn't a big deal at all since it would be hard to accidentally call tmpfd and link the result in a test, where this is meant to be used.

Akram

[1] https://man7.org/linux/man-pages/man2/open.2.html#DESCRIPTION

[2] https://man7.org/linux/man-pages/man2/linkat.2.html