linux-kernel - Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put

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Message-ID: <20191008170652.GU26530@ZenIV.linux.org.uk>
Date:   Tue, 8 Oct 2019 18:06:52 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to
 unsafe_put_user()

On Tue, Oct 08, 2019 at 05:38:31PM +0200, Greg KH wrote:
> On Tue, Oct 08, 2019 at 04:29:00PM +0100, Al Viro wrote:
> > On Tue, Oct 08, 2019 at 03:14:16PM +0200, Greg KH wrote:
> > > On Tue, Oct 08, 2019 at 05:57:12AM +0100, Al Viro wrote:
> > > > 
> > > > 	OK...  BTW, do you agree that the use of access_ok() in
> > > > drivers/tty/n_hdlc.c:n_hdlc_tty_read() is wrong?  It's used as an early
> > > > cutoff, so we don't bother waiting if user has passed an obviously bogus
> > > > address.  copy_to_user() is used for actual copying there...
> > > 
> > > Yes, it's wrong, and not needed.  I'll go rip it out unless you want to?
> > 
> > I'll throw it into misc queue for now; it has no prereqs and nothing is going
> > to depend upon it.
> 
> Great, thanks.
> 
> > While looking for more of the same pattern: usb_device_read().  Frankly,
> > usb_device_dump() calling conventions look ugly - it smells like it
> > would be much happier as seq_file.  Iterator would take some massage,
> > but that seems to be doable.  Anyway, that's a separate story...
> 
> That's just a debugfs file, and yes, it should be moved to seq_file.  I
> think I tried it a long time ago, but given it's just a debugging thing,
> I gave up as it wasn't worth it.
> 
> But yes, the access_ok() there also seems odd, and should be dropped.

I'm almost tempted to keep it there as a reminder/grep fodder ;-)

Seriously, though, it might be useful to have a way of marking the places
in need of gentle repair of retrocranial inversions _without_ attracting
the "checkpatch warning of the week" crowd...