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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Wed, 12 Jun 2019 12:37:49 -0700
Message-ID: <CAPcyv4hn0Vz24s5EWKr39roXORtBTevZf7dDutH+jwapgV3oSw@mail.gmail.com>
Subject: Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()
To:     Qian Cai <cai@lca.pw>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.de>,
        Linux MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Jun 12, 2019 at 12:16 PM Qian Cai <cai@lca.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@lca.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@intel.com>

...but why is pfn_to_online_page() a multi-line macro instead of a
static inline like all the helper routines it invokes?