ext4: add check for inodes_count overflow in new resize ioctl

Addresses-Red-Hat-Bugzilla: #913245

Reported-by: Eric Sandeen <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>
Reviewed-by: Carlos Maiolino <[email protected]>
Cc: [email protected]

Author: tytso

fs/ext4/resize.c

@@ -1882,6 +1882,10 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 		return 0;
 
 	n_group = ext4_get_group_number(sb, n_blocks_count - 1);
+	if (n_group > (0xFFFFFFFFUL / EXT4_INODES_PER_GROUP(sb))) {
+		ext4_warning(sb, "resize would cause inodes_count overflow");
+		return -EINVAL;
+	}
 	ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);
 
 	n_desc_blocks = num_desc_blocks(sb, n_group + 1);