Re: [PATCH 1/2] Btrfs: fix clone vs chattr NODATASUM race

[Nikolay Borisov <nborisov@suse.com>]

On 23.05.2018 01:02, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> In btrfs_clone_files(), we must check the NODATASUM flag while the
> inodes are locked. Otherwise, it's possible that btrfs_ioctl_setflags()
> will change the flags after we check and we can end up with a party
> checksummed file.
> 
> Fixes: 0e7b824c4ef9 ("Btrfs: don't make a file partly checksummed through file clone")
> Signed-off-by: Omar Sandoval <osandov@fb.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/ioctl.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index cf0d3bc6f625..784e267aad32 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4280,11 +4280,6 @@ static noinline int btrfs_clone_files(struct file *file, struct file *file_src,
>  	    src->i_sb != inode->i_sb)
>  		return -EXDEV;
>  
> -	/* don't make the dst file partly checksummed */
> -	if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
> -	    (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
> -		return -EINVAL;
> -
>  	if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode))
>  		return -EISDIR;
>  
> @@ -4294,6 +4289,13 @@ static noinline int btrfs_clone_files(struct file *file, struct file *file_src,
>  		inode_lock(src);
>  	}
>  
> +	/* don't make the dst file partly checksummed */
> +	if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
> +	    (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
>  	/* determine range to clone */
>  	ret = -EINVAL;
>  	if (off + len > src->i_size || off + len < off)
>