On Sat, Mar 6, 2021 at 12:50 AM Andrew Morton akpm@linux-foundation.org wrote:
On Sat, 6 Mar 2021 00:36:33 +0100 Andrey Konovalov andreyknvl@google.com wrote:
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.
...
--- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page,
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, fpi_flags);/* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should@@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page,
debug_pagealloc_unmap_pages(page, 1 << order);
kasan_free_nondeferred_pages(page, order, fpi_flags);return true;}
kasan_free_nondeferred_pages() has only two args in current mainline.
Ah, yes, forgot to mention: this goes on top of:
kasan: initialize shadow to TAG_INVALID for SW_TAGS mm, kasan: don't poison boot memory with tag-based modes
I fixed that in the obvious manner...
Thanks!
If you changed this patch, you'll also need to change the other one though.