On 9/11/23 15:24, Yin Fengwei wrote:
> Hi Matthew,
>
> On 9/10/23 11:02, Matthew Wilcox wrote:
>> On Sat, Sep 09, 2023 at 10:12:48AM -0700, syzbot wrote:
>>> commit 617c28ecab22d98a3809370eb6cb50fa24b7bfe1
>>> Author: Yin Fengwei <fengwei.yin@xxxxxxxxx>
>>> Date: Wed Aug 2 15:14:05 2023 +0000
>>>
>>> filemap: batch PTE mappings
>>
>> Hmm ... I don't know if this is the bug, but ...
> I do think we should merge your patch here. LKP already noticed some performance
> regressions. I suppose this patch can fix some of them.
I will verify this patch to see whether the regressions noticed by LKP can be
fixed. Will keep you updated for any progress. Thanks.
Regards
Yin, Fengwei
>
>
> I root caused the this "bad page map" issue in my local env. It's related with pte
> with protnone on x86_64. So if pte is not protnone, advancing pte by adding
> 1UL << PFN_PTE_SHIFT is correct. But if pte is protnone, should subtract
> 1UL << PFN_PTE_SHIFT. I saw pfn_pte() had pfn ^= protnone_mask() and just realized
> it.
>
>
> The producer mmap with PROT_NONE and then trigger SIGXFSZ and create core file.
> That will cause GUP with FOLL_FORCE and create protnone pte.
>
> I submitted request to sysbot to test the fixing worked on my local env. Thanks.
>
>
> Regards
> Yin, Fengwei
>
>>
>> #syz test
>>
>> diff --git a/mm/filemap.c b/mm/filemap.c
>> index 582f5317ff71..580d0b2b1a7c 100644
>> --- a/mm/filemap.c
>> +++ b/mm/filemap.c
>> @@ -3506,7 +3506,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
>> if (count) {
>> set_pte_range(vmf, folio, page, count, addr);
>> folio_ref_add(folio, count);
>> - if (in_range(vmf->address, addr, count))
>> + if (in_range(vmf->address, addr, count * PAGE_SIZE))
>> ret = VM_FAULT_NOPAGE;
>> }
>>
>> @@ -3520,7 +3520,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
>> if (count) {
>> set_pte_range(vmf, folio, page, count, addr);
>> folio_ref_add(folio, count);
>> - if (in_range(vmf->address, addr, count))
>> + if (in_range(vmf->address, addr, count * PAGE_SIZE))
>> ret = VM_FAULT_NOPAGE;
>> }
>>
>>
