[src/trunk]: src/sbin/newfs Explicitly zap possible Ext2fs magic leftover to ...

[tsutsui <tsutsui%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/574a5083264f
branches:  trunk
changeset: 773577:574a5083264f
user:      tsutsui <tsutsui%NetBSD.org@localhost>
date:      Tue Feb 07 14:14:45 2012 +0000

description:
Explicitly zap possible Ext2fs magic leftover to prevent
kernel vfs_mountroot() and bootloaders from mis-recognizing
the newfs(8)'ed file system as still Ext2fs.

The problem is reported and the fix is tested by Frank Wille
on current-users@.  Also approved by releng.

diffstat:

 sbin/newfs/mkfs.c |  12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diffs (40 lines):

diff -r ef60ffcdfa83 -r 574a5083264f sbin/newfs/mkfs.c
--- a/sbin/newfs/mkfs.c Tue Feb 07 11:40:24 2012 +0000
+++ b/sbin/newfs/mkfs.c Tue Feb 07 14:14:45 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mkfs.c,v 1.110 2011/08/25 16:17:58 joerg Exp $ */
+/*     $NetBSD: mkfs.c,v 1.111 2012/02/07 14:14:45 tsutsui Exp $       */
 
 /*
  * Copyright (c) 1980, 1989, 1993
@@ -73,7 +73,7 @@
 #if 0
 static char sccsid[] = "@(#)mkfs.c     8.11 (Berkeley) 5/3/95";
 #else
-__RCSID("$NetBSD: mkfs.c,v 1.110 2011/08/25 16:17:58 joerg Exp $");
+__RCSID("$NetBSD: mkfs.c,v 1.111 2012/02/07 14:14:45 tsutsui Exp $");
 #endif
 #endif /* not lint */
 
@@ -152,6 +152,8 @@
        ((sblock.fs_magic == FS_UFS1_MAGIC) ? \
        (dp)->dp1.di_##field : (dp)->dp2.di_##field)
 
+#define EXT2FS_SBOFF   1024    /* XXX: SBOFF in <ufs/ext2fs/ext2fs.h> */
+
 char *iobuf;
 int iobufsize;                 /* size to end of 2nd inode block */
 int iobuf_memsize;             /* Actual buffer size */
@@ -615,6 +617,12 @@
                        for (sz = SBLOCKSIZE; sz <= 0x10000; sz <<= 1)
                                zap_old_sblock(roundup(sblkoff, sz));
                }
+               /*
+                * Also zap possible Ext2fs magic leftover to prevent
+                * kernel vfs_mountroot() and bootloaders from mis-recognizing
+                * this file system as Ext2fs.
+                */
+               zap_old_sblock(EXT2FS_SBOFF);
 
                if (isappleufs) {
                        struct appleufslabel appleufs;