linux-kernel - Re: [PATCH v2 05/17] compat_ioctl: move more drivers to generic_compat_ioctl

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Message-ID: <20180914203506.GE35251@wrath>
Date:   Fri, 14 Sep 2018 13:35:06 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        qat-linux@...el.com, linux-crypto@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, amd-gfx@...ts.freedesktop.org,
        linux-input@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-nvme@...ts.infradead.org, linux-pci@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-fbdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-btrfs@...r.kernel.org, ceph-devel@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 05/17] compat_ioctl: move more drivers to
 generic_compat_ioctl_ptrarg

On Wed, Sep 12, 2018 at 05:08:52PM +0200, Arnd Bergmann wrote:
> The .ioctl and .compat_ioctl file operations have the same prototype so
> they can both point to the same function, which works great almost all
> the time when all the commands are compatible.
> 
> One exception is the s390 architecture, where a compat pointer is only
> 31 bit wide, and converting it into a 64-bit pointer requires calling
> compat_ptr(). Most drivers here will ever run in s390, but since we now
> have a generic helper for it, it's easy enough to use it consistently.
> 
> I double-checked all these drivers to ensure that all ioctl arguments
> are used as pointers or are ignored, but are not interpreted as integer
> values.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
...
>  drivers/platform/x86/wmi.c                  | 2 +-
...
>  static void link_event_work(struct work_struct *work)
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 04791ea5d97b..e4d0697e07d6 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -886,7 +886,7 @@ static const struct file_operations wmi_fops = {
>  	.read		= wmi_char_read,
>  	.open		= wmi_char_open,
>  	.unlocked_ioctl	= wmi_ioctl,
> -	.compat_ioctl	= wmi_ioctl,
> +	.compat_ioctl	= generic_compat_ioctl_ptrarg,
>  };

For platform/drivers/x86:

Acked-by: Darren Hart (VMware) <dvhart@...radead.org>

As for a longer term solution, would it be possible to init fops in such
a way that the compat_ioctl call defaults to generic_compat_ioctl_ptrarg
so we don't have to duplicate this boilerplate for every ioctl fops
structure?

-- 
Darren Hart
VMware Open Source Technology Center