Re: [syzbot] WARNING in iomap_iter

Matthew Wilcox
2022-08-22T14:52:46Z

On Mon, Aug 22, 2022 at 08:19:43PM +0530, Siddh Raman Pant wrote:
> On Mon, 22 Aug 2022 20:15:28 +0530 Matthew Wilcox wrote:
> > On Sun, Aug 21, 2022 at 05:18:16PM +0530, Siddh Raman Pant wrote:
> > > @@ -979,9 +979,15 @@ loop_set_status_from_info(struct loop_device *lo,
> > >
> > > lo->lo_offset = info->lo_offset;
> > > lo->lo_sizelimit = info->lo_sizelimit;
> > > + lo->lo_flags = info->lo_flags;
> > > +
> > > + /* loff_t/int vars are assigned __u64/__u32 vars (respectively) */
> > > + if (lo->lo_offset < 0 || lo->lo_sizelimit < 0 || lo->lo_flags < 0)
> > > + return -EOVERFLOW;
> >
> > Why would you check lo_flags? That really, really should be an unsigned
> > type.
>
> I agree, but the loop_device struct has (see line 54 of loop.c):
> int lo_flags;
>
> Thus, I checked for it, as we are not changing any types.

But it's not an integer. It's a bitfield. Nobody checks lo_flags for
"is it less than zero". That makes it very different from lo_offset.