MiNT 1.09: some protection for biosfs

[Andreas Schwab <schwab@lamothe.informatik.uni-dortmund.de>]

Most of the function of biosfs that change it should only be allowed
by root, IMHO.  This patch adds checks to bios_remove, bios_rename,
bios_fscntl and bios_symlink. Additionally i have added a check for
existence of the new name in bios_rename.

--- orig/biosfs.c	Tue Aug 17 21:23:18 1993
+++ biosfs.c	Mon Nov 22 19:58:30 1993
@@ -358,6 +358,9 @@
 	struct bios_file *b, **lastb;
 
 	UNUSED(dir);
+	if (curproc->euid)
+	  return EACCDN;
+
 	lastb = &broot;
 	for (b = broot; b; b = *(lastb = &b->next)) {
 		if (!stricmp(b->name, name)) break;
@@ -401,18 +404,24 @@
 	fcookie *newdir;
 	const char *newname;
 {
-	struct bios_file *b;
+	struct bios_file *b, *be = 0;
 
 	UNUSED(olddir); UNUSED(newdir);
 
-/* BUG: we should check to see if "newname" already exists */
+	if (curproc->euid)
+	  return EACCDN;
 
 	for (b = broot; b; b = b->next) {
-		if (!stricmp(b->name, oldname)) {
-			strncpy(b->name, newname, BNAME_MAX);
-			return 0;
-		}
-	}
+		if (!stricmp (b->name, newname))
+		  return EACCDN;
+		if (!stricmp(b->name, oldname))
+		  be = b;
+	}
+	if (be)
+	  {
+	    strncpy(be->name, newname, BNAME_MAX);
+	    return 0;
+	  }
 	return EFILNF;
 }
 
@@ -552,6 +561,9 @@
 	struct bios_file *b;
 
 	UNUSED(dir);
+	if (curproc->euid)
+	  return EACCDN;
+
 	if ((unsigned)cmd == DEV_INSTALL) {
 		struct dev_descr *d = (struct dev_descr *)arg;
 
@@ -608,6 +620,9 @@
 	struct bios_file *b;
 	long r;
 	fcookie fc;
+
+	if (curproc->euid)
+	  return EACCDN;
 
 	r = bios_lookup(dir, name, &fc);
 	if (r == 0) return EACCDN;	/* file already exists */