don't allow removal of /. more robust approach involving stat this time.

posix uses the language "resolves to the root directory" in this case.
ok millert

2 files changed, 13 insertions, 4 deletions

diff --git a/bin/rm/rm.1 b/bin/rm/rm.1
index d04e4873272..5c8aefaab7d 100644
--- a/bin/rm/rm.1
+++ b/bin/rm/rm.1
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: rm.1,v 1.39 2015/10/13 04:30:53 daniel Exp $
+.\"	$OpenBSD: rm.1,v 1.40 2016/04/15 23:09:57 tedu Exp $
 .\"	$NetBSD: rm.1,v 1.8 1995/07/25 19:37:30 jtc Exp $
 .\"
 .\" Copyright (c) 1990, 1993, 1994
@@ -33,7 +33,7 @@
 .\"
 .\"	@(#)rm.1	8.5 (Berkeley) 12/5/94
 .\"
-.Dd $Mdocdate: October 13 2015 $
+.Dd $Mdocdate: April 15 2016 $
 .Dt RM 1
 .Os
 .Sh NAME
@@ -101,7 +101,7 @@ The
 .Nm
 utility removes symbolic links, not the files referenced by the links.
 .Pp
-It is an error to attempt to remove the files
+It is an error to attempt to remove the root directory or the files
 .Dq \&.
 or
 .Dq .. .
diff --git a/bin/rm/rm.c b/bin/rm/rm.c
index f9c19549d5f..2f919ffad9c 100644
--- a/bin/rm/rm.c
+++ b/bin/rm/rm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rm.c,v 1.36 2016/02/01 22:34:19 gsoares Exp $	*/
+/*	$OpenBSD: rm.c,v 1.37 2016/04/15 23:09:57 tedu Exp $	*/
 /*	$NetBSD: rm.c,v 1.19 1995/09/07 06:48:50 jtc Exp $	*/
 
 /*-
@@ -395,9 +395,17 @@ checkdot(char **argv)
 {
 	char *p, **save, **t;
 	int complained;
+	struct stat sb, root;
 
+	stat("/", &root);
 	complained = 0;
 	for (t = argv; *t;) {
+		if (lstat(*t, &sb) == 0 &&
+		    root.st_ino == sb.st_ino && root.st_dev == sb.st_dev) {
+			if (!complained++)
+				warnx("\"/\" may not be removed");
+			goto skip;
+		}
 		/* strip trailing slashes */
 		p = strrchr(*t, '\0');
 		while (--p > *t && *p == '/')
@@ -412,6 +420,7 @@ checkdot(char **argv)
 		if (ISDOT(p)) {
 			if (!complained++)
 				warnx("\".\" and \"..\" may not be removed");
+skip:
 			eval = 1;
 			for (save = t; (t[0] = t[1]) != NULL; ++t)
 				continue;