+ mm-fix-page-reference-leak-in-soft_offline_page.patch added to -mm tree

The patch titled
     Subject: mm: fix page reference leak in soft_offline_page()
has been added to the -mm tree.  Its filename is
     mm-fix-page-reference-leak-in-soft_offline_page.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-fix-page-reference-leak-in-soft_offline_page.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-page-reference-leak-in-soft_offline_page.patch

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Dan Williams <redacted>
Subject: mm: fix page reference leak in soft_offline_page()

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.

Link: https://lkml.kernel.org/r/161058501210.1840162.8108917599181157327.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn")
Signed-off-by: Dan Williams <redacted>
Reviewed-by: David Hildenbrand <redacted>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Naoya Horiguchi <redacted>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qian Cai <redacted>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |   20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

--- a/mm/memory-failure.c~mm-fix-page-reference-leak-in-soft_offline_page
+++ a/mm/memory-failure.c

@@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct
 	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
 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;
 	}
 

_

Patches currently in -mm which might be from dan.j.williams@intel.com are

mm-fix-page-reference-leak-in-soft_offline_page.patch
mm-move-pfn_to_online_page-out-of-line.patch
mm-teach-pfn_to_online_page-to-consider-subsection-validity.patch
mm-teach-pfn_to_online_page-about-zone_device-section-collisions.patch
mm-fix-memory_failure-handling-of-dax-namespace-metadata.patch