btrfs: fix invalid-free in btrfs_extent_same

If this condition ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
		   (BTRFS_I(dst)->flags & BTRFS_INODE_NODATASUM))
is hit, we will go to free the uninitialized cmp.src_pages and
cmp.dst_pages.

Fixes: 67b07bd4 ("Btrfs: reuse cmp workspace in EXTENT_SAME ioctl")
Signed-off-by: NLu Fengqi <lufq.fnst@cn.fujitsu.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -3577,7 +3577,7 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
 		ret = btrfs_extent_same_range(src, loff, BTRFS_MAX_DEDUPE_LEN,
 					      dst, dst_loff, &cmp);
 		if (ret)
-			goto out_unlock;
+			goto out_free;
 
 		loff += BTRFS_MAX_DEDUPE_LEN;
 		dst_loff += BTRFS_MAX_DEDUPE_LEN;
@@ -3587,16 +3587,16 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
 		ret = btrfs_extent_same_range(src, loff, tail_len, dst,
 					      dst_loff, &cmp);
 
+out_free:
+	kvfree(cmp.src_pages);
+	kvfree(cmp.dst_pages);
+
 out_unlock:
 	if (same_inode)
 		inode_unlock(src);
 	else
 		btrfs_double_inode_unlock(src, dst);
 
-out_free:
-	kvfree(cmp.src_pages);
-	kvfree(cmp.dst_pages);
-
 	return ret;
 }