Re: [RFC PATCH v2 3/3] xfs: Fix x32 ioctls when cmd numbers differ from ia32.

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Dec 14, 2018 at 08:22:59PM -0500, Nick Bowler wrote:
> Several ioctl structs change size between native 32-bit (ia32) and x32
> applications, because x32 follows the native 64-bit (amd64) integer
> alignment rules and uses 64-bit time_t.  In these instances, the ioctl
> number changes so userspace simply gets -ENOTTY.  This scenario can be
> handled by simply adding more cases.
> 
> Looking at the different ioctls implemented here:
> 
> - All the ones marked 'No size or alignment issue on any arch' should
>   presumably all be fine.
> 
> - All the ones under BROKEN_X86_ALIGNMENT are different under integer
>   alignment rules.  Since x32 matches amd64 here, we just need both
>   sets of cases handled.
> 
> - XFS_IOC_SWAPEXT has both integer alignment differences and time_t
>   differences.  Since x32 matches amd64 here, we need to add a case
>   which calls the native implementation.
> 
> - The remaining ioctls have neither 64-bit integers nor time_t, so
>   x32 matches ia32 here and no change is required at this level.  The
>   bulkstat ioctl implementations have some pointer chasing which is
>   handled separately.
> 
> Signed-off-by: Nick Bowler <nbowler@draconx.ca>

Looks mostly ok to me, provided they don't drop x32 this release.

(It doesn't sound to me like that's going to happen any time soon...)

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

(Will try to test all this... /me flexes his cross-arch muscles...)

--D

> ---
>  fs/xfs/xfs_ioctl32.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index 1cdc75dca779..bd9ffad0f65e 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -579,8 +579,12 @@ xfs_file_compat_ioctl(
>  	case FS_IOC_GETFSMAP:
>  	case XFS_IOC_SCRUB_METADATA:
>  		return xfs_file_ioctl(filp, cmd, p);
> -#ifndef BROKEN_X86_ALIGNMENT
> -	/* These are handled fine if no alignment issues */
> +#if !defined(BROKEN_X86_ALIGNMENT) || defined(CONFIG_X86_X32)
> +	/*
> +	 * These are handled fine if no alignment issues.  To support x32
> +	 * which uses native 64-bit alignment we must emit these cases in
> +	 * addition to the ia-32 compat set below.
> +	 */
>  	case XFS_IOC_ALLOCSP:
>  	case XFS_IOC_FREESP:
>  	case XFS_IOC_RESVSP:
> @@ -593,8 +597,16 @@ xfs_file_compat_ioctl(
>  	case XFS_IOC_FSGROWFSDATA:
>  	case XFS_IOC_FSGROWFSRT:
>  	case XFS_IOC_ZERO_RANGE:
> +#ifdef CONFIG_X86_X32
> +	/*
> +	 * x32 special: this gets a different cmd number from the ia-32 compat
> +	 * case below; the associated data will match native 64-bit alignment.
> +	 */
> +	case XFS_IOC_SWAPEXT:
> +#endif
>  		return xfs_file_ioctl(filp, cmd, p);
> -#else
> +#endif
> +#if defined(BROKEN_X86_ALIGNMENT)
>  	case XFS_IOC_ALLOCSP_32:
>  	case XFS_IOC_FREESP_32:
>  	case XFS_IOC_ALLOCSP64_32:
> -- 
> 2.16.1
>