From: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
Naoya Horiguchi <nao.horiguchi@gmail.com>,
Michal Hocko <mhocko@kernel.org>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 4/5] mm: Fix page reference leak in soft_offline_page()
Date: Thu, 14 Jan 2021 01:49:45 +0000 [thread overview]
Message-ID: <20210114014944.GA16873@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <161058501210.1840162.8108917599181157327.stgit@dwillia2-desk3.amr.corp.intel.com>
On Wed, Jan 13, 2021 at 04:43:32PM -0800, Dan Williams wrote:
> The conversion to move pfn_to_online_page() internal to
> soft_offline_page() missed that the get_user_pages() reference taken by
> the madvise() path needs to be dropped when pfn_to_online_page() fails.
> Note the direct sysfs-path to soft_offline_page() does not perform a
> get_user_pages() lookup.
>
> When soft_offline_page() is handed a pfn_valid() &&
> !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to
> a leaked reference.
>
> Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
I'm OK if we don't have any other better approach, but the proposed changes
make code a little messy, and I feel that get_user_pages() might be the
right place to fix. Is get_user_pages() expected to return struct page with
holding refcount for offline valid pages? I thought that such pages are
only used by drivers for dax-devices, but that might be wrong. Can I ask for
a little more explanation from this perspective?
Thanks,
Naoya Horiguchi
> ---
> mm/memory-failure.c | 20 ++++++++++++++++----
> 1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 5a38e9eade94..78b173c7190c 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct page *page)
> return rc;
> }
>
> +static void put_ref_page(struct page *page)
> +{
> + if (page)
> + put_page(page);
> +}
> +
> /**
> * soft_offline_page - Soft offline a page.
> * @pfn: pfn to soft-offline
> @@ -1910,20 +1916,26 @@ static int soft_offline_free_page(struct page *page)
> int soft_offline_page(unsigned long pfn, int flags)
> {
> int ret;
> - struct page *page;
> bool try_again = true;
> + struct page *page, *ref_page = NULL;
> +
> + WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED));
>
> if (!pfn_valid(pfn))
> return -ENXIO;
> + if (flags & MF_COUNT_INCREASED)
> + ref_page = pfn_to_page(pfn);
> +
> /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
> page = pfn_to_online_page(pfn);
> - if (!page)
> + if (!page) {
> + put_ref_page(ref_page);
> return -EIO;
> + }
>
> if (PageHWPoison(page)) {
> pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
> - if (flags & MF_COUNT_INCREASED)
> - put_page(page);
> + put_ref_page(ref_page);
> return 0;
> }
>
>
next prev parent reply other threads:[~2021-01-14 1:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 0:43 [PATCH v4 0/5] mm: Fix pfn_to_online_page() with respect to ZONE_DEVICE Dan Williams
2021-01-14 0:43 ` [PATCH v4 1/5] mm: Move pfn_to_online_page() out of line Dan Williams
2021-01-20 10:11 ` Michal Hocko
2021-01-14 0:43 ` [PATCH v4 2/5] mm: Teach pfn_to_online_page() to consider subsection validity Dan Williams
2021-01-20 10:24 ` Michal Hocko
2021-01-14 0:43 ` [PATCH v4 3/5] mm: Teach pfn_to_online_page() about ZONE_DEVICE section collisions Dan Williams
2021-01-20 10:30 ` Michal Hocko
2021-01-14 0:43 ` [PATCH v4 4/5] mm: Fix page reference leak in soft_offline_page() Dan Williams
2021-01-14 1:49 ` HORIGUCHI NAOYA(堀口 直也) [this message]
2021-01-14 6:18 ` Dan Williams
2021-01-14 6:30 ` Oscar Salvador
2021-01-14 7:10 ` HORIGUCHI NAOYA(堀口 直也)
2021-01-17 22:01 ` Andrew Morton
2021-01-17 22:35 ` Dan Williams
2021-01-14 0:43 ` [PATCH v4 5/5] mm: Fix memory_failure() handling of dax-namespace metadata Dan Williams
2021-01-14 2:25 ` HORIGUCHI NAOYA(堀口 直也)
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