Re: BUG: divide error in ubi_attach_mtd_dev

[Zhihao Cheng]

Hi
> Yu Hao,
>
> ----- Ursprüngliche Mail -----
> > Von: "Yu Hao" <yhao016@xxxxxxx>
> > > ubi: mtd0 is already attached to ubi0
> > > ubi7: attaching mtd147
> > > divide error: 0000 [#1] PREEMPT SMP KASAN
> > > CPU: 0 PID: 20023 Comm: syz-executor.0 Not tainted 6.2.0 #6
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > 1.13.0-1ubuntu1.1 04/01/2014
> > > RIP: 0010:mtd_div_by_eb include/linux/mtd/mtd.h:580 [inline]
> > > RIP: 0010:io_init drivers/mtd/ubi/build.c:620 [inline]
> > > RIP: 0010:ubi_attach_mtd_dev+0x77f/0x2fe0 drivers/mtd/ubi/build.c:955
> > > Code: fc ff df 48 c1 ea 03 0f b6 14 02 4c 89 f0 83 e0 07 83 c0 03 38
> > > d0 7c 08 84 d2 0f 85 1f 25 00 00 41 8b 4c 24 10 48 89 d8 31 d2 <48> f7
> > > f1 48 89 c3 e8 b6 f3 1b fc 48 8d 85 40 17 00 00 48 89 c2 48
> > > RSP: 0018:ffffc9000be0fd30 EFLAGS: 00010246
> > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> > > RDX: 0000000000000000 RSI: ffff888047a49d40 RDI: 0000000000000002
> > > RBP: ffff888024e1c000 R08: 0000000000000016 R09: fffff520017c1f47
> > > R10: ffffc9000be0fa37 R11: fffff520017c1f46 R12: ffff88806545a000
> > > R13: 0000000000000000 R14: ffff88806545a010 R15: 0000000000000007
> > > FS:  00007fd45e85c700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
> > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 00007f64aeef53a4 CR3: 000000004f39a000 CR4: 0000000000350ef0
> > > Call Trace:
> > >   <TASK>
> > >   ctrl_cdev_ioctl+0x303/0x3a0 drivers/mtd/ubi/cdev.c:1043
>
> What kind of MTD you attaching?
> Has it erasesize 0?

Yes, I agree with Richard's point, I guess UBI got an mtd device with 
zero erasesize.


 568 static inline uint32_t mtd_div_by_eb(uint64_t sz, struct mtd_info 
*mtd)
 569 {
 570         if (mtd->erasesize_shift)       // erasesize_shift is 0
 571                 return sz >> mtd->erasesize_shift;
 572         do_div(sz, mtd->erasesize);    // erasesize is 0 too
 573         return sz;
 574 }

Yu Hao, how do you find the problem, by syzkaller? Can you provide the 
reproducing program or reproducing log?