From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: kasan, page_alloc: init memory of skipped pages on free
Since commit 7a3b83537188 ("kasan: use separate (un)poison implementation
for integrated init"), when all init, kasan_has_integrated_init(), and
skip_kasan_poison are true, free_pages_prepare() doesn't initialize the
page. This is wrong.
Fix it by remembering whether kasan_poison_pages() performed
initialization, and call kernel_init_free_pages() if it didn't.
Reordering kasan_poison_pages() and kernel_init_free_pages() is OK, since
kernel_init_free_pages() can handle poisoned memory.
Link: https://lkml.kernel.org/r/1d97df75955e52727a3dc1c4e33b3b50506fc3fd.1643047180.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Acked-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
--- a/mm/page_alloc.c~kasan-page_alloc-init-memory-of-skipped-pages-on-free
+++ a/mm/page_alloc.c
@@ -1371,11 +1371,16 @@ static __always_inline bool free_pages_p
* With hardware tag-based KASAN, memory tags must be set before the
* page becomes unavailable via debug_pagealloc or arch_free_page.
*/
- if (init && !kasan_has_integrated_init())
- kernel_init_free_pages(page, 1 << order);
- if (!skip_kasan_poison)
+ if (!skip_kasan_poison) {
kasan_poison_pages(page, order, init);
+ /* Memory is already initialized if KASAN did it internally. */
+ if (kasan_has_integrated_init())
+ init = false;
+ }
+ if (init)
+ kernel_init_free_pages(page, 1 << order);
+
/*
* arch_free_page() can make the page's contents inaccessible. s390
* does this. So nothing which can access the page's contents should
_
