Fix overflow in superblock. From FreeBSD.

FreeBSD's log:
> The ffs superblock includes a 128-byte region for use by temporary
> in-core pointers to summary information. An array in this region
> (fs_csp) could overflow on filesystems with a very large number of
> cylinder groups (~16000 on i386 with 8k blocks). When this happens,
> other fields in the superblock get corrupted, and fsck refuses to
> check the filesystem.
>
> Solve this problem by replacing the fs_csp array in 'struct fs'
> with a single pointer, and add padding to keep the length of the
> 128-byte region fixed. Update the kernel and userland utilities
> to use just this single pointer.
>
> With this change, the kernel no longer makes use of the superblock
> fields 'fs_csshift' and 'fs_csmask'. Add a comment to newfs/mkfs.c
> to indicate that these fields must be calculated for compatibility
> with older kernels.

art@ ok.

1 files changed, 8 insertions, 2 deletions

diff --git a/sbin/newfs/mkfs.c b/sbin/newfs/mkfs.c
index 2368e523f98..aacecf48349 100644
--- a/sbin/newfs/mkfs.c
+++ b/sbin/newfs/mkfs.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mkfs.c,v 1.16 2001/04/04 22:06:38 gluk Exp $	*/
+/*	$OpenBSD: mkfs.c,v 1.17 2001/04/13 02:39:06 gluk Exp $	*/
 /*	$NetBSD: mkfs.c,v 1.25 1995/06/18 21:35:38 cgd Exp $	*/
 
 /*
@@ -38,7 +38,7 @@
 #if 0
 static char sccsid[] = "@(#)mkfs.c	8.3 (Berkeley) 2/3/94";
 #else
-static char rcsid[] = "$OpenBSD: mkfs.c,v 1.16 2001/04/04 22:06:38 gluk Exp $";
+static char rcsid[] = "$OpenBSD: mkfs.c,v 1.17 2001/04/13 02:39:06 gluk Exp $";
 #endif
 #endif /* not lint */
 
@@ -576,6 +576,12 @@ next:
 	sblock.fs_csaddr = cgdmin(&sblock, 0);
 	sblock.fs_cssize =
 	    fragroundup(&sblock, sblock.fs_ncg * sizeof(struct csum));
+
+	/*
+	 * The superblock fields 'fs_csmask' and 'fs_csshift' are no
+	 * longer used. However, we still initialise them so that the
+	 * filesystem remains compatible with old kernels.
+	 */
 	i = sblock.fs_bsize / sizeof(struct csum);
 	sblock.fs_csmask = ~(i - 1);
 	for (sblock.fs_csshift = 0; i > 1; i >>= 1)