Re: [PATCH] nsfs: add compat ioctl handler

[Al Viro]

On Sun, Dec 18, 2022 at 09:07:25PM +0000, Thomas Weißschuh wrote:
> As all parameters and return values of the ioctls have the same
> representation on both 32bit and 64bit we can reuse the normal ioctl
> handler for the compat handler.
> 
> All nsfs ioctls return a plain "int" filedescriptor which is a signed
> 4-byte integer type on both 32bit and 64bit.
> The only parameter taken is by NS_GET_OWNER_UID and is a pointer to a
> "uid_t" which is a 4-byte unsigned integer type on both 32bit and 64bit.
> 
> Fixes: 6786741dbf99 ("nsfs: add ioctl to get an owning user namespace for ns file descriptor")
> Reported-By: Karel Zak <kzak@xxxxxxxxxx>
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>

NAK.  This is broken on s390; use compat_ptr_ioctl instead.