drivers/base/memory.c: don't access uninitialized memmaps in soft_offline_page_store()

Uninitialized memmaps contain garbage and in the worst case trigger kernel
BUGs, especially with CONFIG_PAGE_POISONING.  They should not get touched.

Right now, when trying to soft-offline a PFN that resides on a memory
block that was never onlined, one gets a misleading error with
CONFIG_PAGE_POISONING:

  :/# echo 5637144576 > /sys/devices/system/memory/soft_offline_page
  [   23.097167] soft offline: 0x150000 page already poisoned

But the actual result depends on the garbage in the memmap.

soft_offline_page() can only work with online pages, it returns -EIO in
case of ZONE_DEVICE.  Make sure to only forward pages that are online
(iow, managed by the buddy) and, therefore, have an initialized memmap.

Add a check against pfn_to_online_page() and similarly return -EIO.

Link: http://lkml.kernel.org/r/20191010141200.8985-1-david@redhat.com
Fixes: 542db0a8566d ("mm, memory_hotplug: do not associate hotadded memory to zones until online")	[visible after 4e55b6a92d7a1]
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: <stable@vger.kernel.org>	[4.13+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 6bea4f3f8040dd77c87cf34647b26515061a76a1..55907c27075b13295c05ed197fa7f087546452d1 100644 (file)
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -540,6 +540,9 @@ static ssize_t soft_offline_page_store(struct device *dev,
        pfn >>= PAGE_SHIFT;
        if (!pfn_valid(pfn))
                return -ENXIO;
+       /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
+       if (!pfn_to_online_page(pfn))
+               return -EIO;
        ret = soft_offline_page(pfn_to_page(pfn), 0);
        return ret == 0 ? count : ret;
 }