btrfs: add checks for sys_chunk_array sizes

Verify that possible minimum and maximum size is set, validity of
contents is checked in btrfs_read_sys_array.
Signed-off-by: NDavid Sterba <dsterba@suse.cz>
Signed-off-by: NChris Mason <clm@fb.com>

fs/btrfs/disk-io.c

@@ -3910,6 +3910,25 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
 		ret = -EINVAL;
 	}
 
+	/*
+	 * Obvious sys_chunk_array corruptions, it must hold at least one key
+	 * and one chunk
+	 */
+	if (btrfs_super_sys_array_size(sb) > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
+		printk(KERN_ERR "BTRFS: system chunk array too big %u > %u\n",
+				btrfs_super_sys_array_size(sb),
+				BTRFS_SYSTEM_CHUNK_ARRAY_SIZE);
+		ret = -EINVAL;
+	}
+	if (btrfs_super_sys_array_size(sb) < sizeof(struct btrfs_disk_key)
+			+ sizeof(struct btrfs_chunk)) {
+		printk(KERN_ERR "BTRFS: system chunk array too small %u < %lu\n",
+				btrfs_super_sys_array_size(sb),
+				sizeof(struct btrfs_disk_key)
+				+ sizeof(struct btrfs_chunk));
+		ret = -EINVAL;
+	}
+
 	/*
 	 * The generation is a global counter, we'll trust it more than the others
 	 * but it's still possible that it's the one that's wrong.