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   1 From 641fe2e9387a36f9ee01d7c69382d1fe147a5e98 Mon Sep 17 00:00:00 2001
   2 From: David Hildenbrand <david@redhat.com>
   3 Date: Fri, 18 Oct 2019 20:19:16 -0700
   4 Subject: drivers/base/memory.c: don't access uninitialized memmaps in soft_offline_page_store()
   5
   6 From: David Hildenbrand <david@redhat.com>
   7
   8 commit 641fe2e9387a36f9ee01d7c69382d1fe147a5e98 upstream.
   9
  10 Uninitialized memmaps contain garbage and in the worst case trigger kernel
  11 BUGs, especially with CONFIG_PAGE_POISONING.  They should not get touched.
  12
  13 Right now, when trying to soft-offline a PFN that resides on a memory
  14 block that was never onlined, one gets a misleading error with
  15 CONFIG_PAGE_POISONING:
  16
  17   :/# echo 5637144576 > /sys/devices/system/memory/soft_offline_page
  18   [   23.097167] soft offline: 0x150000 page already poisoned
  19
  20 But the actual result depends on the garbage in the memmap.
  21
  22 soft_offline_page() can only work with online pages, it returns -EIO in
  23 case of ZONE_DEVICE.  Make sure to only forward pages that are online
  24 (iow, managed by the buddy) and, therefore, have an initialized memmap.
  25
  26 Add a check against pfn_to_online_page() and similarly return -EIO.
  27
  28 Link: http://lkml.kernel.org/r/20191010141200.8985-1-david@redhat.com
  29 Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")      [visible after d0dc12e86b319]
  30 Signed-off-by: David Hildenbrand <david@redhat.com>
  31 Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
  32 Acked-by: Michal Hocko <mhocko@suse.com>
  33 Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  34 Cc: "Rafael J. Wysocki" <rafael@kernel.org>
  35 Cc: <stable@vger.kernel.org>    [4.13+]
  36 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  37 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  38 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  39
  40 ---
  41  drivers/base/memory.c |    3 +++
  42  1 file changed, 3 insertions(+)
  43
  44 --- a/drivers/base/memory.c
  45 +++ b/drivers/base/memory.c
  46 @@ -554,6 +554,9 @@ store_soft_offline_page(struct device *d
  47         pfn >>= PAGE_SHIFT;
  48         if (!pfn_valid(pfn))
  49                 return -ENXIO;
  50 +       /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
  51 +       if (!pfn_to_online_page(pfn))
  52 +               return -EIO;
  53         ret = soft_offline_page(pfn_to_page(pfn), 0);
  54         return ret == 0 ? count : ret;
  55  }