Re: [PATCH v2 21/27] compat_ioctl: move cdrom commands into cdrom.c

From: Arnd Bergmann <arnd@arndb.de>
To: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: Jens Axboe <axboe@kernel.dk>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-scsi <linux-scsi@vger.kernel.org>,
	linux-block <linux-block@vger.kernel.org>,
	y2038 Mailman List <y2038@lists.linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 21/27] compat_ioctl: move cdrom commands into cdrom.c
Date: Thu, 19 Dec 2019 13:15:02 +0100	[thread overview]
Message-ID: <CAK8P3a3W+5RTa5jTunotZyV=hgXTxJaPqz_5kJnsdbvSZZPmjg@mail.gmail.com> (raw)
In-Reply-To: <5826d31fcf2fcbe25bf2396e32df3df7d585dd99.camel@codethink.co.uk>

On Wed, Dec 18, 2019 at 9:11 PM Ben Hutchings
<ben.hutchings@codethink.co.uk> wrote:
>
> On Tue, 2019-12-17 at 23:17 +0100, Arnd Bergmann wrote:
> [...]
> > @@ -1710,6 +1711,38 @@ static int idecd_ioctl(struct block_device *bdev, fmode_t mode,
> >       return ret;
> >  }
> >
> > +#ifdef CONFIG_COMPAT
> > +static int idecd_locked_compat_ioctl(struct block_device *bdev, fmode_t mode,
> > +                     unsigned int cmd, unsigned long arg)
> > +{
> > +     struct cdrom_info *info = ide_drv_g(bdev->bd_disk, cdrom_info);
> > +     int err;
> > +
> > +     switch (cmd) {
> > +     case CDROMSETSPINDOWN:
> > +             return idecd_set_spindown(&info->devinfo, arg);
> > +     case CDROMGETSPINDOWN:
> > +             return idecd_get_spindown(&info->devinfo, arg);
>
> compat_ptr() should also be applied to the argument for these two
> commands, though I'm fairly sure IDE drivers have never been useful on
> s390 so it doesn't matter in practice.

Agreed on both, fixed by folding in this change:

diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index 2de6e8ace957..e09b949a7c46 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -1716,19 +1716,20 @@ static int idecd_locked_compat_ioctl(struct
block_device *bdev, fmode_t mode,
                        unsigned int cmd, unsigned long arg)
 {
        struct cdrom_info *info = ide_drv_g(bdev->bd_disk, cdrom_info);
+       void __user *argp = compat_ptr(arg);
        int err;

        switch (cmd) {
        case CDROMSETSPINDOWN:
-               return idecd_set_spindown(&info->devinfo, arg);
+               return idecd_set_spindown(&info->devinfo, (unsigned long)argp);
        case CDROMGETSPINDOWN:
-               return idecd_get_spindown(&info->devinfo, arg);
+               return idecd_get_spindown(&info->devinfo, (unsigned long)argp);
        default:
                break;
        }

        return cdrom_ioctl(&info->devinfo, bdev, mode, cmd,
-                          (unsigned long)compat_ptr(arg));
+                          (unsigned long)argp);
 }

static int idecd_compat_ioctl(struct block_device *bdev, fmode_t mode,

Unfortunately the generic_ide_ioctl() call still needs an unconverted arg,
so I can't just use compat_ptr() to call the native idecd_locked_ioctl()
for all commands.

Thanks,

       Arnd
