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Subject[PATCH] mm, vmstat: Fix NULL pointer dereference during pagetypeinfo print
Date
During showing the pagetypeinfo, we forgot to save the found page
and dereference a invalid page address from the stack.

To fix it, save and reference the page address returned by
pfn_to_online_page().

Signed-off-by: Firo Yang <firogm@gmail.com>
---
mm/vmstat.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index c432e58..6dae6b2 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1223,7 +1223,8 @@ static void pagetypeinfo_showblockcount_print(struct seq_file *m,
for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
struct page *page;

- if (!pfn_to_online_page(pfn))
+ page = pfn_to_online_page(pfn);
+ if (!page)
continue;

/* Watch for unexpected holes punched in the memmap */
--
2.9.4
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