Re: [syzbot] WARNING in __vmalloc_node_range

[Dmitry Vyukov]

On Thu, May 6, 2021 at 4:57 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> 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?