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From: Oscar Salvador <osalvador@suse.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>,
	David Hildenbrand <david@redhat.com>,
	vishal.l.verma@intel.com, linux-nvdimm@lists.01.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/5] mm: Teach pfn_to_online_page() about ZONE_DEVICE section collisions
Date: Tue, 12 Jan 2021 12:00:28 +0100	[thread overview]
Message-ID: <20210112110028.GB12956@linux> (raw)
In-Reply-To: <161044409294.1482714.434561066315039753.stgit@dwillia2-desk3.amr.corp.intel.com>

On Tue, Jan 12, 2021 at 01:34:53AM -0800, Dan Williams wrote:
> While pfn_to_online_page() is able to determine pfn_valid() at
> subsection granularity it is not able to reliably determine if a given
> pfn is also online if the section is mixes ZONE_{NORMAL,MOVABLE} with
> ZONE_DEVICE. This means that pfn_to_online_page() may return invalid
> @page objects. For example with a memory map like:
> 
> 100000000-1fbffffff : System RAM
>   142000000-143002e16 : Kernel code
>   143200000-143713fff : Kernel rodata
>   143800000-143b15b7f : Kernel data
>   144227000-144ffffff : Kernel bss
> 1fc000000-2fbffffff : Persistent Memory (legacy)
>   1fc000000-2fbffffff : namespace0.0
> 
> This command:
> 
> echo 0x1fc000000 > /sys/devices/system/memory/soft_offline_page
> 
> ...succeeds when it should fail. When it succeeds it touches
> an uninitialized page and may crash or cause other damage (see
> dissolve_free_huge_page()).

[...]
 
> Because the collision case is rare, and for simplicity, the
> SECTION_TAINT_ZONE_DEVICE flag is never cleared once set.
> 
> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Reported-by: Michal Hocko <mhocko@suse.com>
> Reported-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

-- 
Oscar Salvador
SUSE L3

  parent reply	other threads:[~2021-01-12 11:01 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-12  9:34 [PATCH v2 0/5] mm: Fix pfn_to_online_page() with respect to ZONE_DEVICE Dan Williams
2021-01-12  9:34 ` [PATCH v2 1/5] mm: Move pfn_to_online_page() out of line Dan Williams
2021-01-12  9:46   ` David Hildenbrand
2021-01-12 10:19   ` Oscar Salvador
2021-01-12  9:34 ` [PATCH v2 2/5] mm: Teach pfn_to_online_page() to consider subsection validity Dan Williams
2021-01-12  9:53   ` David Hildenbrand
2021-01-12 10:48     ` Oscar Salvador
2021-01-12 22:20     ` Dan Williams
2021-01-12  9:34 ` [PATCH v2 3/5] mm: Teach pfn_to_online_page() about ZONE_DEVICE section collisions Dan Williams
2021-01-12 10:01   ` David Hildenbrand
2021-01-12 11:00   ` Oscar Salvador [this message]
2021-01-12  9:34 ` [PATCH v2 4/5] mm: Fix page reference leak in soft_offline_page() Dan Williams
2021-01-12  9:53   ` Oscar Salvador
2021-01-12 20:03     ` Dan Williams
2021-01-12 10:16   ` David Hildenbrand
2021-01-12  9:35 ` [PATCH v2 5/5] libnvdimm/namespace: Fix visibility of namespace resource attribute Dan Williams

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