Re: BUG: divide error in ubi_attach_mtd_dev

[Zhihao Cheng]

在 2023/4/23 16:02, Richard Weinberger 写道:
> ----- Ursprüngliche Mail -----
> > Von: "chengzhihao1" <chengzhihao1@xxxxxxxxxx>
> > > > root@syzkaller:~# cat /proc/mtd
> > > > dev:    size   erasesize  name
> > > > mtd0: 00020000 00001000 “mtdram test device”
> > >
> > > Hmm, mtdram should be fine, erasesize is not zero.
> >
> > I guess the zero-erasesize mtd device is dynamically generated in
> > runtime, after looking through the code, I find erasesize is
> > initiallized in specific flash driver and it won't be updated later(eg.
> > ioctl\sysctl). And some mtd devices may have zero erasesize, eg.
> > drivers/mtd/devices/mchp23k256.c[1]. Unfortunately, I don't know how to
> > load/simulate this mtd, maybe it requires a real device? If we load this
> > mtd device as ubi, it will trigger the problem?
>
> Indeed. I guess qemu can emulate such chips.
> So better fix UBI to reject attaching of mtd's with erasesize being 0.
> (Please note, we cannot test for MTD_NO_ERASE, this one means there is no
> erase method).

Phram is an exception, it has erase function but is set flag 
'MTD_CAP_RAM'. May I interpret 'MTD_NO_ERASE' as erase function is not 
necessary?