[src/trunk]: src/sys/ufs/ffs ffs_reload(): the current implementation blindly...

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

details:   https://anonhg.NetBSD.org/src/rev/92d2e30799b3
branches:  trunk
changeset: 806634:92d2e30799b3
user:      maxv <maxv%NetBSD.org@localhost>
date:      Tue Mar 03 17:46:39 2015 +0000

description:
ffs_reload(): the current implementation blindly guesses critical fields
of the superblock didn't change. Add checks to ensure they didn't change
for real. This prevents several memory corruptions.

diffstat:

 sys/ufs/ffs/ffs_vfsops.c |  24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diffs (52 lines):

diff -r dd9602943d23 -r 92d2e30799b3 sys/ufs/ffs/ffs_vfsops.c
--- a/sys/ufs/ffs/ffs_vfsops.c  Tue Mar 03 14:31:48 2015 +0000
+++ b/sys/ufs/ffs/ffs_vfsops.c  Tue Mar 03 17:46:39 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ffs_vfsops.c,v 1.319 2015/02/23 13:38:54 maxv Exp $    */
+/*     $NetBSD: ffs_vfsops.c,v 1.320 2015/03/03 17:46:39 maxv Exp $    */
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ffs_vfsops.c,v 1.319 2015/02/23 13:38:54 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ffs_vfsops.c,v 1.320 2015/03/03 17:46:39 maxv Exp $");
 
 #if defined(_KERNEL_OPT)
 #include "opt_ffs.h"
@@ -733,12 +733,6 @@
 #endif
                fs->fs_flags &= ~FS_SWAPPED;
 
-       /* We don't want the superblock size to change. */
-       if (newfs->fs_sbsize != fs_sbsize) {
-               brelse(bp, 0);
-               kmem_free(newfs, fs_sbsize);
-               return (EINVAL);
-       }
        if ((newfs->fs_magic != FS_UFS1_MAGIC &&
             newfs->fs_magic != FS_UFS2_MAGIC)) {
                brelse(bp, 0);
@@ -751,6 +745,20 @@
                return (EINVAL);
        }
 
+       /*
+        * The current implementation doesn't handle the possibility that
+        * these values may have changed.
+        */
+       if ((newfs->fs_sbsize != fs_sbsize) ||
+           (newfs->fs_cssize != fs->fs_cssize) ||
+           (newfs->fs_contigsumsize != fs->fs_contigsumsize) ||
+           (newfs->fs_ncg != fs->fs_ncg)) {
+               brelse(bp, 0);
+               kmem_free(newfs, fs_sbsize);
+               return (EINVAL);
+       }
+
+
        /* Store off old fs_sblockloc for fs_oldfscompat_read. */
        sblockloc = fs->fs_sblockloc;
        /*