mm/memory-failure.c: don't access uninitialized memmaps in memory_failure()

We should check for pfn_to_online_page() to not access uninitialized
memmaps.  Reshuffle the code so we don't have to duplicate the error
message.

Link: http://lkml.kernel.org/r/20191009142435.3975-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")	[visible after d0dc12e86b319]
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@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/mm/memory-failure.c b/mm/memory-failure.c
index 0ae72b6..3151c87 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1257,17 +1257,19 @@ int memory_failure(unsigned long pfn, int flags)
        if (!sysctl_memory_failure_recovery)
                panic("Memory failure on page %lx", pfn);
 
-       if (!pfn_valid(pfn)) {
+       p = pfn_to_online_page(pfn);
+       if (!p) {
+               if (pfn_valid(pfn)) {
+                       pgmap = get_dev_pagemap(pfn, NULL);
+                       if (pgmap)
+                               return memory_failure_dev_pagemap(pfn, flags,
+                                                                 pgmap);
+               }
                pr_err("Memory failure: %#lx: memory outside kernel control\n",
                        pfn);
                return -ENXIO;
        }
 
-       pgmap = get_dev_pagemap(pfn, NULL);
-       if (pgmap)
-               return memory_failure_dev_pagemap(pfn, flags, pgmap);
-
-       p = pfn_to_page(pfn);
        if (PageHuge(p))
                return memory_failure_hugetlb(pfn, flags);
        if (TestSetPageHWPoison(p)) {