linux-kernel - Re: [PATCH next] vt: fix a warning when kmalloc alloc large memory

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Message-ID: <nycvar.YSQ.7.76.2003281218470.2671@knanqh.ubzr>
Date:   Sat, 28 Mar 2020 12:20:01 -0400 (EDT)
From:   Nicolas Pitre <nico@...xnic.net>
To:     Adam Borowski <kilobyte@...band.pl>
cc:     Chen Wandun <chenwandun@...wei.com>, jslaby@...e.com,
        gregkh@...uxfoundation.org, daniel.vetter@...ll.ch,
        sam@...nborg.org, b.zolnierkie@...sung.com, lukas@...ner.de,
        ghalat@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] vt: fix a warning when kmalloc alloc large memory

On Sat, 28 Mar 2020, Adam Borowski wrote:

> On Fri, Mar 27, 2020 at 10:55:14PM -0400, Nicolas Pitre wrote:
> > On Sat, 28 Mar 2020, Chen Wandun wrote:
> > 
> > > If the memory size that use kmalloc() to allocate exceed MAX_ORDER pages,
> > > it will hit the WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)), so add memory
> > > allocation flag __GFP_NOWARN to silence a warning, othervise, it will
> > > cause panic if panic_on_warn is enable.
> > 
> > Wow! How do you manage that? You need something like a 1024x1024 text 
> > screen to get such a big memory allocation.
> 
> ioctl(VT_RESIZE) allows up to 32767x32767, unprivileged for a local user.
> That's 4GB per console.

Right. And that's ridiculous. This ought to be limited to something much 
saner.


Nicolas