fix for minix crash

[Andries.Brouwer]

Mounting a (corrupt) minix filesystem with zero s_zmap_blocks
gives a spectacular crash on my 2.6.17.8 system, no doubt
because minix/inode.c does an unconditional
	minix_set_bit(0,sbi->s_zmap[0]->b_data);
Here a fix (against 2.6.17.8).

Andries

diff -uprN -X /linux/dontdiff a/fs/minix/inode.c b/fs/minix/inode.c
--- a/fs/minix/inode.c	2006-08-07 16:01:12.000000000 +0200
+++ b/fs/minix/inode.c	2006-08-22 11:15:53.000000000 +0200
@@ -204,6 +204,8 @@ static int minix_fill_super(struct super
 	/*
 	 * Allocate the buffer map to keep the superblock small.
 	 */
+	if (sbi->s_imap_blocks == 0 || sbi->s_zmap_blocks == 0)
+		goto out_illegal_sb;
 	i = (sbi->s_imap_blocks + sbi->s_zmap_blocks) * sizeof(bh);
 	map = kmalloc(i, GFP_KERNEL);
 	if (!map)
@@ -276,6 +278,11 @@ out_no_map:
 		printk("MINIX-fs: can't allocate map\n");
 	goto out_release;
 
+out_illegal_sb:
+	if (!silent)
+		printk("MINIX-fs: bad superblock\n");
+	goto out_release;
+
 out_no_fs:
 	if (!silent)
 		printk("VFS: Can't find a Minix or Minix V2 filesystem "
-
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