linux-kernel - Re: [PATCH v2] vt: don't use kmalloc() for the unicode screen buffer

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Date:   Tue, 31 Mar 2020 11:30:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     Sam Ravnborg <sam@...nborg.org>, Nicolas Pitre <nico@...xnic.net>,
        Chen Wandun <chenwandun@...wei.com>,
        Adam Borowski <kilobyte@...band.pl>,
        Jiri Slaby <jslaby@...e.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Lukas Wunner <lukas@...ner.de>, ghalat@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] vt: don't use kmalloc() for the unicode screen buffer

On Tue, Mar 31, 2020 at 10:43:11AM +0200, Daniel Vetter wrote:
> On Mon, Mar 30, 2020 at 9:08 PM Sam Ravnborg <sam@...nborg.org> wrote:
> >
> > Hi Nicolas
> >
> > On Sat, Mar 28, 2020 at 10:25:11PM -0400, Nicolas Pitre wrote:
> > > Even if the actual screen size is bounded in vc_do_resize(), the unicode
> > > buffer is still a little more than twice the size of the glyph buffer
> > > and may exceed MAX_ORDER down the kmalloc() path. This can be triggered
> > > from user space.
> > >
> > > Since there is no point having a physically contiguous buffer here,
> > > let's avoid the above issue as well as reducing pressure on high order
> > > allocations by using vmalloc() instead.
> > >
> > > Signed-off-by: Nicolas Pitre <nico@...xnic.net>
> > > Cc: <stable@...r.kernel.org>
> > >
> > > ---
> > >
> > > Changes since v1:
> > >
> > > - Added missing include, found by kbuild test robot.
> > >   Strange that my own build doesn't complain.
> >
> > When I did the drmP.h removal vmalloc was one of the header files
> > that turned up missing in many cases - but only for some architectures.
> > I learned to include alpha in the build.
> > If it survived building for alpha then I had fixed the majority
> > of the issues related to random inherited includes.
> >
> > The patch itself looks good.
> >
> > Acked-by: Sam Ravnborg <sam@...nborg.org>
> 
> Greg, I'm assuming you'll pick this up through the tty tree? I kinda
> want to stop the habit of merging vt patches, maybe then
> get_maintainers will stop thinking I'm responsible somehow :-)

Yes, I'll take it, and have been taking vt patches for a few releases
now so don't worry, you aren't responsible anymore :)

thanks,

greg k-h