Function path_has_dotdot_component

syscall.c:1679–1694

Returns 1 if path has any "/"-separated component that is exactly * "..", 0 otherwise. Used by secure_relative_open's front-door * validation to reject inputs that the per-component walk fallback * would otherwise resolve through ".." -- e.g. bare "..", "foo/..", * "subdir/.." -- which RESOLVE_BENEATH-equivalent kernels reject in * the kernel but the per-component fallback (NetBSD/OpenBSD/Sol

 * the kernel but the per-component fallback (NetBSD/OpenBSD/Solaris/
 * Cygwin/pre-5.6 Linux) does not. */
static int path_has_dotdot_component(const char *path)
{
	const char *p = path;

	while (*p) {
		const char *q;
		if (*p == '/') { p++; continue; }
		q = p;
		while (*q && *q != '/')
			q++;
		if (q - p == 2 && p[0] == '.' && p[1] == '.')
			return 1;
		p = q;
	}
	return 0;
}

#if defined(__linux__) && defined(HAVE_OPENAT2)
/* openat2(RESOLVE_BENEATH) via the raw syscall, gated on openat2_usable() so a