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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 18 Dec 2019 23:17:47 +0100
Message-ID: <CAK8P3a28Qn22Cx-bVhY5rjZVuhRXE2Jb0rezCozAhC0DZqxcUg@mail.gmail.com>
Subject: Re: [PATCH v2 23/27] compat_ioctl: move HDIO ioctl handling into drivers/ide
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>,
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        Christoph Hellwig <hch@lst.de>,
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On Wed, Dec 18, 2019 at 10:11 PM Ben Hutchings
<ben.hutchings@codethink.co.uk> wrote:
> On Tue, 2019-12-17 at 23:17 +0100, Arnd Bergmann wrote:
> > Most of the HDIO ioctls are only used by the obsolete drivers/ide
> > subsystem, these can be handled by changing ide_cmd_ioctl() to be aware
> > of compat mode and doing the correct transformations in place and using
> > it as both native and compat handlers for all drivers.
> >
> > The SCSI drivers implementing the same commands are already doing
> > this in the drivers, so the compat_blkdev_driver_ioctl() function
> > is no longer needed now.
> >
> > The BLKSECTSET and HDIO_GETGEO_BIG ioctls are not implemented
> > in any driver any more and no longer need any conversion.
> [...]
>
> I noticed that HDIO_DRIVE_TASKFILE, handled by ide_taskfile_ioctl() in
> drivers/ide/ide-taskfile.c, never had compat handling before.  After
> this patch it does, but its argument isn't passed through compat_ptr().
> Again, doesn't really matter because IDE isn't a thing on s390.

I checked again, and I think it's worse than that: ide_taskfile_ioctl()
takes an ide_task_request_t argument, which is not compatible
at all (it has two long members). I suspect what happened here
is that I confused it with ide_cmd_ioctl(), which takes a 'struct
ide_taskfile' argument that /is/ compatible.

I don't think there is a point in adding a handler now: most
users of drivers/ide are 32-bit only, and nobody complained
so far, but I would add this change if you agree:

diff --git a/drivers/ide/ide-ioctls.c b/drivers/ide/ide-ioctls.c
index f6497c817493..83afee3983fe 100644
--- a/drivers/ide/ide-ioctls.c
+++ b/drivers/ide/ide-ioctls.c
@@ -270,6 +270,9 @@ int generic_ide_ioctl(ide_drive_t *drive, struct
block_device *bdev,
        case HDIO_DRIVE_TASKFILE:
                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                        return -EACCES;
+               /* missing compat handler for HDIO_DRIVE_TASKFILE */
+               if (in_compat_syscall())
+                       return -ENOTTY;
                if (drive->media == ide_disk)
                        return ide_taskfile_ioctl(drive, arg);
                return -ENOMSG;


         Arnd