On Fri, 5 Feb 2016 08:06:12 +0100 Dmitry Vyukov <dvyu...@google.com> wrote:
> On Thu, Feb 4, 2016 at 11:11 PM, David Rientjes <rient...@google.com> wrote: > > On Thu, 4 Feb 2016, Dmitry Vyukov wrote: > > > >> Size of kmalloc() in vc_do_resize() is controlled by user. > >> Too large kmalloc() size triggers WARNING message on console. > >> > >> Use __GFP_NOWARN for this kmalloc() to not scare admins. > >> > > > > Hmm, this is hitting the WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)) for > > order >= MAX_ORDER. > > > > vc_do_resize() has > > > > if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW) > > return -EINVAL; > > > > so the appropriate fix would seem to be to reject sizes that would exceed > > the page allocator's ability to return contiguous memory (MAX_ORDER) > > rather than ever trying the allocation in the first place. > > Hi David, > > Please see Alan response to original report here: > https://groups.google.com/d/msg/syzkaller/ufjvr5j0URo/lTlpYP0DBQAJ > I can't say that I fully understand it. I think we can go down to something like cols * lines < 4MB with complete safety. Alan
