Re: [PATCH v2 2/2] xfs: add static size checks for ioctl UABI

[Wilfred Mallawa]

On Tue, 2026-02-10 at 15:59 +1000, Wilfred Mallawa wrote:
> From: Wilfred Mallawa <wilfred.mallawa@xxxxxxx>
> 
> The ioctl structures in libxfs/xfs_fs.h are missing static size
> checks.
> It is useful to have static size checks for these structures as
> adding
> new fields to them could cause issues (e.g. extra padding that may be
> inserted by the compiler). So add these checks to xfs/xfs_ondisk.h.
> 
> Due to different padding/alignment requirements across different
> architectures, to avoid build failures, some structures are ommited
> from
> the size checks. For example, structures with "compat_" definitions
> in
> xfs/xfs_ioctl32.h are ommited.
> 
> Signed-off-by: Wilfred Mallawa <wilfred.mallawa@xxxxxxx>
> ---
> V1 -> V2:
> 	- Added inline comment to describe why some ioctl structs
> 	  are not addded.
> 
> 	- Keep the new size check coupled under "ioctl UABI".
> 
> 	- Drop size checks for structures that are in
> xfs/xfs_ioctl32.h
> 	  (i.e compat__X) to avoid build failures across different
> 	  architectures.
> ---
>  fs/xfs/libxfs/xfs_ondisk.h | 40 +++++++++++++++++++++++++++++++++---
> --
>  1 file changed, 35 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_ondisk.h b/fs/xfs/libxfs/xfs_ondisk.h
> index 601a8367ced6..dced91d281fa 100644
> --- a/fs/xfs/libxfs/xfs_ondisk.h
> +++ b/fs/xfs/libxfs/xfs_ondisk.h
> @@ -208,11 +208,6 @@ xfs_check_ondisk_structs(void)
>  	XFS_CHECK_OFFSET(struct xfs_dir3_free, hdr.hdr.magic,	0);
>  	XFS_CHECK_OFFSET(struct xfs_attr3_leafblock, hdr.info.hdr,
> 0);
>  
> -	XFS_CHECK_STRUCT_SIZE(struct
> xfs_bulkstat,		192);
> -	XFS_CHECK_STRUCT_SIZE(struct xfs_inumbers,		24);
> -	XFS_CHECK_STRUCT_SIZE(struct xfs_bulkstat_req,		64);
> -	XFS_CHECK_STRUCT_SIZE(struct xfs_inumbers_req,		64);
> -
>  	/*
>  	 * Make sure the incore inode timestamp range corresponds to
> hand
>  	 * converted values based on the ondisk format
> specification.
> @@ -292,6 +287,41 @@ xfs_check_ondisk_structs(void)
>  	XFS_CHECK_SB_OFFSET(sb_pad,			281);
>  	XFS_CHECK_SB_OFFSET(sb_rtstart,			288)
> ;
>  	XFS_CHECK_SB_OFFSET(sb_rtreserved,		296);
> +
> +	/*
> +	 * ioctl UABI
> +	 *
> +	 * Due to different padding/alignment requirements across
> +	 * different architectures, some structures are ommited from
> +	 * the size checks. In addition, structures with
> architecture
> +	 * dependent size fields are also ommited (e.g.
> __kernel_long_t).
> +	 */
> +	XFS_CHECK_STRUCT_SIZE(struct
> xfs_bulkstat,		192);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_inumbers,		24);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_bulkstat_req,		64);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_inumbers_req,		64);
> +	XFS_CHECK_STRUCT_SIZE(struct dioattr,			12);
> +	XFS_CHECK_STRUCT_SIZE(struct getbmap,			32);
> +	XFS_CHECK_STRUCT_SIZE(struct getbmapx,			48);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_attrlist_cursor,	16);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_attrlist,		8);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_attrlist,		8);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_attrlist_ent,		4);
> +	XFS_CHECK_STRUCT_SIZE(struct
> xfs_ag_geometry,		128);
> +	XFS_CHECK_STRUCT_SIZE(struct
> xfs_rtgroup_geometry,	128);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_error_injection,	8);
> +	XFS_CHECK_STRUCT_SIZE(struct
> xfs_fsop_geom,		256);
> +	XFS_CHECK_STRUCT_SIZE(struct
> xfs_fsop_geom_v4,		112);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_fsop_counts,		32);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_fsop_resblks,		16);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_growfs_log,		8);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_bulk_ireq,		64);
> +	XFS_CHECK_STRUCT_SIZE(struct
> xfs_fs_eofblocks,		128);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_fsid,			8);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_scrub_metadata,	64);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_scrub_vec,		16);
> +	XFS_CHECK_STRUCT_SIZE(struct xfs_scrub_vec_head,	40);
> +

Extra white-space here, my bad! Will fixup for V3.

>  }
>  
>  #endif /* __XFS_ONDISK_H */