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Subject[PATCH 5.4 041/104] PM: hibernate: fix crashes with init_on_free=1
Date
From: Alexander Potapenko <glider@google.com>

commit 18451f9f9e5810b8bd1245c5ae166f257e0e2b9d upstream.

Upon resuming from hibernation, free pages may contain stale data from
the kernel that initiated the resume. This breaks the invariant
inflicted by init_on_free=1 that freed pages must be zeroed.

To deal with this problem, make clear_free_pages() also clear the free
pages when init_on_free is enabled.

Fixes: 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options")
Reported-by: Johannes Stezenbach <js@sig21.net>
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: 5.3+ <stable@vger.kernel.org> # 5.3+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/power/snapshot.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1147,24 +1147,24 @@ void free_basic_memory_bitmaps(void)

void clear_free_pages(void)
{
-#ifdef CONFIG_PAGE_POISONING_ZERO
struct memory_bitmap *bm = free_pages_map;
unsigned long pfn;

if (WARN_ON(!(free_pages_map)))
return;

- memory_bm_position_reset(bm);
- pfn = memory_bm_next_pfn(bm);
- while (pfn != BM_END_OF_MAP) {
- if (pfn_valid(pfn))
- clear_highpage(pfn_to_page(pfn));
-
+ if (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) || want_init_on_free()) {
+ memory_bm_position_reset(bm);
pfn = memory_bm_next_pfn(bm);
+ while (pfn != BM_END_OF_MAP) {
+ if (pfn_valid(pfn))
+ clear_highpage(pfn_to_page(pfn));
+
+ pfn = memory_bm_next_pfn(bm);
+ }
+ memory_bm_position_reset(bm);
+ pr_info("free pages cleared after restore\n");
}
- memory_bm_position_reset(bm);
- pr_info("free pages cleared after restore\n");
-#endif /* PAGE_POISONING_ZERO */
}

/**

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