Re: [PATCH 6/6] xfs: refactor all the EFI/EFD log item sizeof logic

[Kees Cook <keescook@chromium.org>]

On Mon, Oct 24, 2022 at 02:33:05PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Refactor all the open-coded sizeof logic for EFI/EFD log item and log
> format structures into common helper functions whose names reflect the
> struct names.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  fs/xfs/libxfs/xfs_log_format.h |   48 ++++++++++++++++++++++++++++
>  fs/xfs/xfs_extfree_item.c      |   69 ++++++++++++----------------------------
>  fs/xfs/xfs_extfree_item.h      |   16 +++++++++
>  fs/xfs/xfs_super.c             |   12 ++-----
>  4 files changed, 88 insertions(+), 57 deletions(-)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_log_format.h b/fs/xfs/libxfs/xfs_log_format.h
> index 2f41fa8477c9..f13e0809dc63 100644
> --- a/fs/xfs/libxfs/xfs_log_format.h
> +++ b/fs/xfs/libxfs/xfs_log_format.h
> @@ -616,6 +616,14 @@ typedef struct xfs_efi_log_format {
>  	xfs_extent_t		efi_extents[];	/* array of extents to free */
>  } xfs_efi_log_format_t;
>  
> +static inline size_t
> +xfs_efi_log_format_sizeof(
> +	unsigned int		nr)
> +{
> +	return sizeof(struct xfs_efi_log_format) +
> +			nr * sizeof(struct xfs_extent);
> +}

These are all just open-coded versions of struct_size(). It's better
to use those, instead, as they will never overflow. (They saturate at
SIZE_MAX.) i.e. what you proposed here:
https://lore.kernel.org/linux-xfs/20210311031745.GT3419940@magnolia/

Otherwise, yeah, looks good.

-Kees

-- 
Kees Cook