linux-kernel - Re: [syzbot] BUG: unable to handle kernel paging request in alloc_huge

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Date:   Mon, 16 Aug 2021 10:00:35 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        syzbot <syzbot+57876cfc2dca0c6b2e6a@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] BUG: unable to handle kernel paging request in
 alloc_huge_page

On 8/16/21 12:47 AM, Dmitry Vyukov wrote:
> On Sun, 15 Aug 2021 at 20:17, Mike Kravetz <mike.kravetz@...cle.com> wrote:
>>
>> On 8/14/21 4:24 PM, Matthew Wilcox wrote:
>>> On Sat, Aug 14, 2021 at 03:06:52PM -0700, Andrew Morton wrote:
>>>> On Sat, 14 Aug 2021 04:07:23 -0700 syzbot <syzbot+57876cfc2dca0c6b2e6a@...kaller.appspotmail.com> wrote:
>>>>> HEAD commit:    92d00774360d Add linux-next specific files for 20210810
>>>>> RIP: 0010:__list_add include/linux/list.h:71 [inline]
>>>>> RIP: 0010:list_add include/linux/list.h:86 [inline]
>>>>> RIP: 0010:alloc_huge_page+0xdcb/0x11b0 mm/hugetlb.c:2821
>>>>
>>>> That appears to be
>>>>
>>>>              list_add(&page->lru, &h->hugepage_activelist);
>>>>
>>>> I'm suspecting Mike's surplus page changes?
>>>
>>> Is this not the same as
>>> https://lore.kernel.org/linux-mm/846c4502-3332-0d25-87f5-cb3b71afc38f@quicinc.com/
>>> which is already patched in your tree?
>>
>> Yes, I believe it is the same, and already fixed.  RCX: fffffffffffffffc
>> makes me 99.9% confident.
> 
> Let's tell syzbot about the fix:
> 
> #syz fix:
> mm/hugetlb: Initialize page to NULL in alloc_buddy_huge_page_with_mpol()
> 

Thanks!

I verified and removed my .01% of doubt.
-- 
Mike Kravetz