linux-kernel - Re: [syzbot] WARNING in __vmalloc_node

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Date:   Thu, 6 May 2021 18:06:55 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        USB list <linux-usb@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] WARNING in __vmalloc_node_range

On Thu, May 06, 2021 at 05:00:41PM +0200, 'Dmitry Vyukov' via syzkaller-bugs wrote:
> On Thu, May 6, 2021 at 4:57 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> >
> > On Thu, May 06, 2021 at 04:22:10PM +0200, Uladzislau Rezki wrote:
> > > Seems like vmalloc() is called with zero size passed:
> > >
> > > <snip>
> > > void *__vmalloc_node_range(unsigned long size, unsigned long align,
> > >                       unsigned long start, unsigned long end, gfp_t gfp_mask,
> > >                       pgprot_t prot, unsigned long vm_flags, int node,
> > >                       const void *caller)
> > > {
> > >       struct vm_struct *area;
> > >       void *addr;
> > >       unsigned long real_size = size;
> > >       unsigned long real_align = align;
> > >       unsigned int shift = PAGE_SHIFT;
> > >
> > > 2873  if (WARN_ON_ONCE(!size))
> > >               return NULL;
> > > <snip>
> > >
> > > from the dvb_dmx_init() driver:
> > >
> > > <snip>
> > > int dvb_dmx_init(struct dvb_demux *dvbdemux)
> > > {
> > >       int i;
> > >       struct dmx_demux *dmx = &dvbdemux->dmx;
> > >
> > >       dvbdemux->cnt_storage = NULL;
> > >       dvbdemux->users = 0;
> > > 1251  dvbdemux->filter = vmalloc(array_size(sizeof(struct dvb_demux_filter),
> > > <snip>                                              dvbdemux->filternum));
> >
> > Indeed.
> >
> > It is a mystery because array_size() should never return less than
> > sizeof(struct dvb_demux_filter).  That's the whole point of the
> > array_size() function is that it returns ULONG_MAX if there is an
> > integer overflow.
> 
> But it will return 0 if dvbdemux->filternum==0, right?
> 

Heh...  I'm an idiot.  I was thinking of struct_size().  Sorry.

regards,
dan carpenter