[PATCH] Avoid disk sector_t overflow for >2TB ext3 filesystem

If ext3 filesystem is larger than 2TB, and sector_t is a u32 (i.e.
CONFIG_LBD not defined in the kernel), the calculation of the disk sector
will overflow.  Add check at ext3_fill_super() and ext3_group_extend() to
prevent mount/remount/resize >2TB ext3 filesystem if sector_t size is 4
bytes.

Verified this patch on a 32 bit platform without CONFIG_LBD defined
(sector_t is 32 bits long), mount refuse to mount a 10TB ext3.

Signed-off-by: Mingming Cao<cmm@us.ibm.com>
Acked-by: NAndreas Dilger <adilger@clusterfs.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/ext3/resize.c

@@ -925,6 +925,16 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es,
 	if (n_blocks_count == 0 || n_blocks_count == o_blocks_count)
 		return 0;
 
+	if (n_blocks_count > (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
+		printk(KERN_ERR "EXT3-fs: filesystem on %s:"
+			" too large to resize to %lu blocks safely\n",
+			sb->s_id, n_blocks_count);
+		if (sizeof(sector_t) < 8)
+			ext3_warning(sb, __FUNCTION__,
+			"CONFIG_LBD not enabled\n");
+		return -EINVAL;
+	}
+
 	if (n_blocks_count < o_blocks_count) {
 		ext3_warning(sb, __FUNCTION__,
 			     "can't shrink FS - resize aborted");

fs/ext3/super.c

@@ -1565,6 +1565,16 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
 		goto failed_mount;
 	}
 
+	if (le32_to_cpu(es->s_blocks_count) >
+		    (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
+		printk(KERN_ERR "EXT3-fs: filesystem on %s:"
+			" too large to mount safely\n", sb->s_id);
+		if (sizeof(sector_t) < 8)
+			printk(KERN_WARNING "EXT3-fs: CONFIG_LBD not "
+					"enabled\n");
+		goto failed_mount;
+	}
+
 	if (EXT3_BLOCKS_PER_GROUP(sb) == 0)
 		goto cantfind_ext3;
 	sbi->s_groups_count = (le32_to_cpu(es->s_blocks_count) -