From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
Dave Hansen <dave.hansen@linux.intel.com>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
torvalds@linux-foundation.org, akpm@linux-foundation.org,
hannes@cmpxchg.org, iamjoonsoo.kim@lge.com,
mgorman@techsingularity.net, tony.luck@intel.com, vbabka@suse.cz,
aarcange@redhat.com, hillf.zj@alibaba-inc.com, hughd@google.com,
oleg@redhat.com, peterz@infradead.org, riel@redhat.com,
srikar@linux.vnet.ibm.com, vdavydov.dev@gmail.com,
mingo@kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, x86@kernel.org
Subject: Re: [mm 4.15-rc8] Random oopses under memory pressure.
Date: Fri, 19 Jan 2018 15:30:51 +0300 [thread overview]
Message-ID: <20180119123051.xd5orkoagxanp23d@black.fi.intel.com> (raw)
In-Reply-To: <20180119120747.GV6584@dhcp22.suse.cz>
On Fri, Jan 19, 2018 at 12:07:47PM +0000, Michal Hocko wrote:
> > >From 861f68c555b87fd6c0ccc3428ace91b7e185b73a Mon Sep 17 00:00:00 2001
> > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> > Date: Thu, 18 Jan 2018 18:24:07 +0300
> > Subject: [PATCH] mm, page_vma_mapped: Drop faulty pointer arithmetics in
> > check_pte()
> >
> > Tetsuo reported random crashes under memory pressure on 32-bit x86
> > system and tracked down to change that introduced
> > page_vma_mapped_walk().
> >
> > The root cause of the issue is the faulty pointer math in check_pte().
> > As ->pte may point to an arbitrary page we have to check that they are
> > belong to the section before doing math. Otherwise it may lead to weird
> > results.
> >
> > It wasn't noticed until now as mem_map[] is virtually contiguous on flatmem or
> > vmemmap sparsemem. Pointer arithmetic just works against all 'struct page'
> > pointers. But with classic sparsemem, it doesn't.
>
> it doesn't because each section memap is allocated separately and so
> consecutive pfns crossing two sections might have struct pages at
> completely unrelated addresses.
Okay, I'll amend it.
> > Let's restructure code a bit and replace pointer arithmetic with
> > operations on pfns.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> > Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>
> The patch makes sense but there is one more thing to fix here.
>
> [...]
> > static bool check_pte(struct page_vma_mapped_walk *pvmw)
> > {
> > + unsigned long pfn;
> > +
> > if (pvmw->flags & PVMW_MIGRATION) {
> > #ifdef CONFIG_MIGRATION
> > swp_entry_t entry;
> > @@ -41,37 +61,34 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
> >
> > if (!is_migration_entry(entry))
> > return false;
> > - if (migration_entry_to_page(entry) - pvmw->page >=
> > - hpage_nr_pages(pvmw->page)) {
> > - return false;
> > - }
> > - if (migration_entry_to_page(entry) < pvmw->page)
> > - return false;
> > +
> > + pfn = migration_entry_to_pfn(entry);
> > #else
> > WARN_ON_ONCE(1);
> > #endif
> > - } else {
>
> now you allow to pass through with uninitialized pfn. We used to return
> true in that case so we should probably keep it in this WARN_ON_ONCE
> case. Please note that I haven't studied this particular case and the
> ifdef is definitely not an act of art but that is a separate topic.
Good catch. Thanks.
I think returning true here is wrong as we don't validate in any way what
is mapped there. I'll put "return false;".
And I take a look if we can drop the #ifdef.
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2018-01-19 12:30 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-05 14:45 [x86? mm? fs? 4.15-rc6] Random oopses by simple write under memory pressure Tetsuo Handa
2018-01-09 10:39 ` [mm? 4.15-rc7] " Tetsuo Handa
2018-01-10 11:49 ` [mm? 4.15-rc7] Random oopses " Tetsuo Handa
2018-01-10 12:45 ` Michal Hocko
2018-01-10 13:37 ` Tetsuo Handa
2018-01-11 13:57 ` Michal Hocko
2018-01-11 14:11 ` Tetsuo Handa
2018-01-11 14:21 ` Michal Hocko
2018-01-11 14:37 ` Tetsuo Handa
2018-01-12 1:31 ` [mm " Tetsuo Handa
2018-01-12 1:42 ` Linus Torvalds
2018-01-12 11:22 ` Tetsuo Handa
2018-01-14 11:54 ` Tetsuo Handa
2018-01-15 23:05 ` Linus Torvalds
2018-01-16 1:15 ` [mm 4.15-rc8] " Tetsuo Handa
2018-01-16 2:14 ` Linus Torvalds
2018-01-16 8:06 ` Dave Hansen
2018-01-16 8:37 ` Ingo Molnar
2018-01-16 19:30 ` Linus Torvalds
2018-01-16 17:33 ` Tetsuo Handa
2018-01-16 19:34 ` Linus Torvalds
2018-01-17 11:08 ` Tetsuo Handa
2018-01-17 21:39 ` Linus Torvalds
2018-01-17 21:51 ` Linus Torvalds
2018-01-17 22:04 ` Dave Hansen
2018-01-17 22:00 ` Dave Hansen
2018-01-17 22:15 ` Linus Torvalds
2018-01-18 8:12 ` Tetsuo Handa
2018-01-18 12:25 ` Kirill A. Shutemov
2018-01-18 13:12 ` Kirill A. Shutemov
2018-01-18 14:34 ` Kirill A. Shutemov
2018-01-18 14:38 ` Dave Hansen
2018-01-18 14:45 ` Kirill A. Shutemov
2018-01-18 14:51 ` Dave Hansen
2018-01-18 16:58 ` Linus Torvalds
2018-01-18 14:45 ` Dave Hansen
2018-01-18 14:58 ` Andrea Arcangeli
2018-01-18 16:56 ` Kirill A. Shutemov
2018-01-18 17:26 ` Luck, Tony
2018-01-18 17:28 ` Linus Torvalds
2018-01-18 17:26 ` Linus Torvalds
2018-01-18 23:49 ` Kirill A. Shutemov
2018-01-19 12:55 ` Matthew Wilcox
2018-01-19 18:42 ` Linus Torvalds
2018-01-19 22:12 ` Al Viro
2018-01-19 22:53 ` Linus Torvalds
2018-01-20 2:02 ` Al Viro
2018-01-20 5:24 ` Al Viro
2018-01-20 9:38 ` Luc Van Oostenryck
2018-01-18 15:40 ` Kirill A. Shutemov
2018-01-18 17:22 ` Michal Hocko
2018-01-19 10:02 ` Kirill A. Shutemov
2018-01-19 10:33 ` Michal Hocko
2018-01-19 11:49 ` Kirill A. Shutemov
2018-01-19 12:07 ` Michal Hocko
2018-01-19 12:30 ` Kirill A. Shutemov [this message]
2018-01-19 2:01 ` Tetsuo Handa
2018-01-11 18:11 ` [mm? 4.15-rc7] " Linus Torvalds
2018-01-11 20:59 ` Tetsuo Handa
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