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Subject: Re: BUG: divide error in ubi_attach_mtd_dev
To:     Richard Weinberger <richard@nod.at>, Yu Hao <yhao016@ucr.edu>
CC:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Vignesh Raghavendra <vigneshr@ti.com>,
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From:   Zhihao Cheng <chengzhihao1@huawei.com>
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Date:   Sun, 23 Apr 2023 11:20:55 +0800
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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