linux-kernel - Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online

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Date:   Wed, 12 Jun 2019 12:38:54 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()

On Wed, Jun 12, 2019 at 12:37 PM Dan Williams <dan.j.williams@...el.com> wrote:
>
> On Wed, Jun 12, 2019 at 12:16 PM Qian Cai <cai@....pw> wrote:
> >
> > The linux-next commit "mm/sparsemem: Add helpers track active portions
> > of a section at boot" [1] causes a crash below when the first kmemleak
> > scan kthread kicks in. This is because kmemleak_scan() calls
> > pfn_to_online_page(() which calls pfn_valid_within() instead of
> > pfn_valid() on x86 due to CONFIG_HOLES_IN_ZONE=n.
> >
> > The commit [1] did add an additional check of pfn_section_valid() in
> > pfn_valid(), but forgot to add it in the above code path.
> >
> > page:ffffea0002748000 is uninitialized and poisoned
> > raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> > raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
> > ------------[ cut here ]------------
> > kernel BUG at include/linux/mm.h:1084!
> > invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> > CPU: 5 PID: 332 Comm: kmemleak Not tainted 5.2.0-rc4-next-20190612+ #6
> > Hardware name: Lenovo ThinkSystem SR530 -[7X07RCZ000]-/-[7X07RCZ000]-,
> > BIOS -[TEE113T-1.00]- 07/07/2017
> > RIP: 0010:kmemleak_scan+0x6df/0xad0
> > Call Trace:
> >  kmemleak_scan_thread+0x9f/0xc7
> >  kthread+0x1d2/0x1f0
> >  ret_from_fork+0x35/0x4
> >
> > [1] https://patchwork.kernel.org/patch/10977957/
> >
> > Signed-off-by: Qian Cai <cai@....pw>
> > ---
> >  include/linux/memory_hotplug.h | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> > index 0b8a5e5ef2da..f02be86077e3 100644
> > --- a/include/linux/memory_hotplug.h
> > +++ b/include/linux/memory_hotplug.h
> > @@ -28,6 +28,7 @@
> >         unsigned long ___nr = pfn_to_section_nr(___pfn);           \
> >                                                                    \
> >         if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr) && \
> > +           pfn_section_valid(__nr_to_section(___nr), pfn) &&      \
> >             pfn_valid_within(___pfn))                              \
> >                 ___page = pfn_to_page(___pfn);                     \
> >         ___page;                                                   \
>
> Looks ok to me:
>
> Acked-by: Dan Williams <dan.j.williams@...el.com>
>
> ...but why is pfn_to_online_page() a multi-line macro instead of a
> static inline like all the helper routines it invokes?

I do need to send out a refreshed version of the sub-section patchset,
so I'll fold this in and give you a Reported-by credit.