Re: BUG: divide error in ubi_attach_mtd_dev

[Zhihao Cheng]

在 2023/4/21 4:36, Richard Weinberger 写道:
> ----- Ursprüngliche Mail -----
> > > Can you please share the qemu command line?
> > qemu-system-x86_64 -m 2G -smp 2 -kernel
> > /home/test/Workspace/SyzGen/linux-distro/linux-6.2-debug/arch/x86/boot/bzImage
> > -append “console=ttyS0 root=/dev/sda net.ifnames=0” -hda
> > /home/test/Workspace/SyzGen/linux-distro/image/stretch.img -chardev
> > socket,id=SOCKSYZ,server=on,nowait,host=localhost,port=54640 -mon
> > chardev=SOCKSYZ,mode=control -device virtio-rng-pci -device
> > e1000,netdev=net0 -netdev
> > user,id=net0,restrict=on,hostfwd=tcp:127.0.0.1:11760-:22 -display none
> > -serial stdio -cpu host,migratable=off -no-reboot -name VM -snapshot
> > -enable-kvm
> >
> > > Within Linux you can query /proc/mtd or /sys/class/mtd/
> > > to get infos about the MTD in question.
> >
> > Thanks for the hints. We find that this is a “mtdram test device”.
> >
> > 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?


[1] https://cloud.tencent.com/developer/ask/sof/114616431