btrfs: tree-checker: validate number of chunk stripes and parity

commit 85d07fb upstream.

If there's no parity and num_stripes < ncopies, a crafted image can
trigger a division by zero in calc_stripe_length().

The image was generated through fuzzing.

CC: [email protected] # 5.4+
Reviewed-by: Qu Wenruo <[email protected]>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=209587
Signed-off-by: Daniel Xu <[email protected]>
Signed-off-by: David Sterba <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: danobi

fs/btrfs/tree-checker.c

@@ -577,18 +577,36 @@ int btrfs_check_chunk_valid(struct extent_buffer *leaf,
 	u64 type;
 	u64 features;
 	bool mixed = false;
+	int raid_index;
+	int nparity;
+	int ncopies;
 
 	length = btrfs_chunk_length(leaf, chunk);
 	stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
 	num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
 	sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
 	type = btrfs_chunk_type(leaf, chunk);
+	raid_index = btrfs_bg_flags_to_raid_index(type);
+	ncopies = btrfs_raid_array[raid_index].ncopies;
+	nparity = btrfs_raid_array[raid_index].nparity;
 
 	if (!num_stripes) {
 		chunk_err(leaf, chunk, logical,
 			  "invalid chunk num_stripes, have %u", num_stripes);
 		return -EUCLEAN;
 	}
+	if (num_stripes < ncopies) {
+		chunk_err(leaf, chunk, logical,
+			  "invalid chunk num_stripes < ncopies, have %u < %d",
+			  num_stripes, ncopies);
+		return -EUCLEAN;
+	}
+	if (nparity && num_stripes == nparity) {
+		chunk_err(leaf, chunk, logical,
+			  "invalid chunk num_stripes == nparity, have %u == %d",
+			  num_stripes, nparity);
+		return -EUCLEAN;
+	}
 	if (!IS_ALIGNED(logical, fs_info->sectorsize)) {
 		chunk_err(leaf, chunk, logical,
 		"invalid chunk logical, have %llu should aligned to %u",