From: Andrey Konovalov andreyknvl@google.com Subject: kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC

Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called after debug_pagealloc_unmap_pages(). This causes a crash when debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an unmapped page.

This patch puts kasan_free_nondeferred_pages() before debug_pagealloc_unmap_pages() and arch_free_page(), which can also make the page unavailable.

Link: https://lkml.kernel.org/r/24cd7db274090f0e5bc3adcdc7399243668e3171.161498731... Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS") Signed-off-by: Andrey Konovalov andreyknvl@google.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Vincenzo Frascino vincenzo.frascino@arm.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Alexander Potapenko glider@google.com Cc: Marco Elver elver@google.com Cc: Peter Collingbourne pcc@google.com Cc: Evgenii Stepanov eugenis@google.com Cc: Branislav Rankov Branislav.Rankov@arm.com Cc: Kevin Brodsky kevin.brodsky@arm.com Cc: Christoph Hellwig hch@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/page_alloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/page_alloc.c~kasan-mm-fix-crash-with-hw_tags-and-debug_pagealloc +++ a/mm/page_alloc.c @@ -1282,6 +1282,12 @@ static __always_inline bool free_pages_p kernel_poison_pages(page, 1 << order);

/* + * With hardware tag-based KASAN, memory tags must be set before the + * page becomes unavailable via debug_pagealloc or arch_free_page. + */ + kasan_free_nondeferred_pages(page, order); + + /* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should * happen after this. @@ -1290,8 +1296,6 @@ static __always_inline bool free_pages_p

debug_pagealloc_unmap_pages(page, 1 << order);

- kasan_free_nondeferred_pages(page, order); - return true; }

_