On Thu, Aug 25, 2022 at 01:21:01PM +0000, Liam Howlett wrote:
> * Mark Brown <broonie@xxxxxxxxxx> [220824 20:34]:
> > On Mon, Aug 22, 2022 at 03:06:30PM +0000, Liam Howlett wrote:
> > > From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> > >
> > > Handle overflow checking in count_mm_mlocked_page_nr() differently.
> >
> > Our QA team found that since next-20220823 we're seeing a couple of test
> > failures in the check_mmap_options kselftest on arm64 platforms with MTE
> > that aren't present in mainline:
> >
> > # # FAIL: mprotect not ignoring clear PROT_MTE property
> > # not ok 21 Check clear PROT_MTE flags with private mapping, sync error mode and mmap memory
> > # # FAIL: mprotect not ignoring clear PROT_MTE property
> > # not ok 22 Check clear PROT_MTE flags with private mapping and sync error mode and mmap/mprotect memory
>
> Thanks.
>
> > I bisected this using qemu[1] which landed on 4ceb4bca479d41a
> > ("mm/mprotect: use maple tree navigation instead of vma linked list"),
> > though I'm not 100% sure I trust the specific identification of the
> > commit I'm pretty confident it's at the very least in this series. I've
> > not done any analysis of the failure beyond getting this bisect result.
> >
> > [1] qemu -smp cpus=4 -cpu max -machine virt,gic-version=3,mte=on
>
> This helps a lot. I think your bisect is accurate:
>
> ...
> struct mmu_gather tlb;
> + MA_STATE(mas, ¤t->mm->mm_mt, start, start);
>
> start = untagged_addr(start);
> ...
>
> It looks like I search against the tagged address. I should initialize
> the state to 0 and mas_set(&mas, start) after untagging the address.
>
> I'll send out a patch once I have recreated and verified this is the
> issue.
Thanks. I did a quick test and untagging start seems to fix the issue (I
was wondering why mprotect() returned -ENOMEM when failing).
--
Catalin
