linux-kernel - [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory

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Message-Id: <20191009142435.3975-3-david@redhat.com>
Date:   Wed,  9 Oct 2019 16:24:35 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>
Subject: [PATCH v2 2/2] 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.

Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...nel.org>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory-failure.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 7ef849da8278..e866e6e5660b 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1253,17 +1253,19 @@ 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)) {
-- 
2.21.0