[patch 03/26] mm/memory-failure.c: don't access uninitialized memmaps in memory_failure()

[akpm@linux-foundation.org]

From: David Hildenbrand <david@redhat.com>
Subject: 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>
---

 mm/memory-failure.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/mm/memory-failure.c~mm-memory-failurec-dont-access-uninitialized-memmaps-in-memory_failure
+++ a/mm/memory-failure.c
@@ -1257,17 +1257,19 @@ int memory_failure(unsigned long pfn, in
 	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)) {
_