Patch: disable path sanitization for modules rooted at "/"

When running in daemon mode with a module rooted at "/", it is not possible to "escape" the module.

Not by prefixing a link target with "../../../../../../..".
Not by prefixing a link target with "/" nor "////".

So it seems to me that path sanitization is not useful in this case.  And it breaks stuff.  In particular, I have a file distribution system where large numbers of authenticated users can use rsync in daemon mode as a forced SSH command, authenticating as themselves, and path sanitization damages links like "../../../../../../../etc/localtime" in user directories - which may be dubious in purpose, but which are harmless.  And I am not the arbiter of my users' data in this sense.  Turning on symlink munging of course damages these data even more - I would prefer to not have it damaged at all.

Trivial fix attached.

Thor

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--- clientserver.c~	2022-09-07 00:46:45.217695027 +0000
+++ clientserver.c	2022-09-07 00:46:48.931684755 +0000
@@ -974,8 +974,14 @@ static int rsync_module(int f_in, int f_
 	if (!change_dir(module_chdir, CD_NORMAL))
 		return path_failure(f_out, module_chdir, True);
 	if (module_dirlen || (!use_chroot && !*lp_daemon_chroot()))
-		sanitize_paths = 1;
-
+		/*
+		 * If module_dir is /, it is not possible to "escape"
+		 * the module, and path sanitization can only break
+		 * stuff.
+		 */
+		if (strcmp(module_dir, "/"))
+			sanitize_paths = 1;
+			
 	if ((munge_symlinks = lp_munge_symlinks(module_id)) < 0)
 		munge_symlinks = !use_chroot || module_dirlen;
 	if (munge_symlinks) {