linux-kernel - Re: [PATCHES] tty ioctls cleanups, compat and not only

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Message-ID: <20180913115951.GB2268@kroah.com>
Date:   Thu, 13 Sep 2018 13:59:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHES] tty ioctls cleanups, compat and not only

On Thu, Sep 13, 2018 at 03:31:19AM +0100, Al Viro wrote:
> 	See vfs.git#work.tty-ioctl.  Completely untested, should seriously
> clean the things up wrt compat.  Remaining problems (aside of the bugs
> introduced in it, of course):
> 	* TIOCSERGSTRUCT must die; it's present only in amiserial and it's
> _vile_; look at what it copies out and weep.
> 	* synclink_gt has proper compat handling for its private ioctls;
> other synclink drivers (with the same ioctls) do not.
> 	* dgnc definitely has buggered ioctls - structs full of longs are
> bloody bad idea for passing around.  It's in staging, and I'd say that it
> needs the userland ABI fixed.
> 	* cyclades, rocket, moxa and mxser probably have non-trivial
> problems with their private ioctls; I hadn't looked into those.
> 	* n_gsm needs ->compat_ioctl(); easy to do, I just hadn't done it
> yet.
> 	* ipwireless might or might not need compat_ioctl (PPP stuff in it);
> not sure.
> 	* ldisc private ioctls need more work.  Hadn't gone there yet.
> Generic ioctls should be fine - they never reach ->compat_ioctl() with this
> series.
> 
> 	There's some overlap with patches posted earlier - e.g. I'm fairly
> sure that keyboard ioctl "remove from fs/compat_ioctl.c" part duplicates
> one of yours; I'll be glad to drop and replace such duplicates with already
> posted variants.
> 
> 	Basic idea is to shunt generic ioctls that are reachable only
> via tty_ioctl() very early in tty_compat_ioctl(), separately for those
> that do and do not need compat_ptr().  That already simplifies the hell
> out of ->compat_ioctl() situation - its instances won't ever see those,
> so they can e.g. ignore the behaviour of n_tty_ioctl_helper(); whatever
> they get in cmd won't be accepted by that one.
> 
> 	Next we separate TIOC[SG]SERIAL into a couple of new methods,
> leaving the copyin/copyout to callers.  That allows to take care of
> compat for those in tty_compat_ioctl() *and* actually kills some of
> ->ioctl() instances.
> 
> 	And then there's dead code of all kinds all over the place ;-/
> The oldest one has been alive from Aug 1 1992 to Oct 18 1992 and had
> shambled around ever since (FIONBIO), but there are other examples.
> 10 years dead is better than 26, but still...
> 
> 	Shortlog and diffstat follow, patches in followups...

Thanks a lot for this work.  If you and Arnd want to figure out whose
tree to take it through, I have no objection.

All of these can be marked as:

	Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

if you want to.

greg k-h