Re: [PATCH v7 0/3] md/raid10: fix r10bio width mismatches across reshape

[Chen Cheng]

在 2026/7/27 02:56, Mykola Marzhan 写道:
> Hi Cheng,
> 
> Independent confirmation of the bug this series fixes, in case more
> evidence helps it land.
> 
> While running a KASAN campaign against the llbitmap reshape v2 series
> (base 55b77337 — unrelated to your fix) every raid10 grow under IO hit
> both faces of the width mismatch:
> 
>    BUG: KASAN: slab-out-of-bounds in free_r10bio+0x97/0x110
>    Read of size 8 at addr ffff888149044ec8 by task ksoftirqd/2/28
>     free_r10bio+0x97/0x110
>     raid10_end_write_request+0x260/0x500
>     blk_update_request+0x18b/0x6b0
>    Allocated by task 232:
>     mempool_alloc_noprof+0x108/0x1d0
>     raid10_make_request+0x18b/0x1100
> 
>    BUG: KASAN: slab-out-of-bounds in raid10_make_request+0x214/0x1100
>    Write of size 192 at addr ffff88814da7aa48 by task fio/460
>     __asan_memset+0x23/0x50
>     raid10_make_request+0x214/0x1100
> 
> (192 bytes = 6 x sizeof(struct r10dev) memset into a 4-disk
> allocation.)
> 
> 456 reports across 5 grow cycles (n2, 4->6 disks, four fio randwrite
> jobs) on the plain base kernel. The mempool face matches your 2/3
> exactly: the 256 preallocated r10bios keep the old width, so any
> allocation that dips into the reserve after the grow is a guaranteed
> OOB write, not just a read.
> 
> The storm is dense enough that raid10 grow under IO is not testable
> under KASAN at all right now — which is how we ran into it, and why
> we would like to see this land.
> 
> We plan to run v7 through the same rig and will follow up with the
> result.
> 

Hi Mykola:

Thanks to let me know that, and welcome to report the result and if you 
have any idea, welcome to discuss.

thanks,
Cheng.

> Thanks,
> Mykola