On Fri, Feb 26, 2021 at 2:25 AM Andrey Konovalov <andreyknvl@xxxxxxxxxx> 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(). > > Besides fixing the crash, this also makes the annotation order consistent > with debug_pagealloc_map_pages() preceding kasan_alloc_pages(). > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > --- > mm/page_alloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c89e7b107514..54bc237fd319 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1311,10 +1311,14 @@ static __always_inline bool free_pages_prepare(struct page *page, > */ > arch_free_page(page, order); > > - debug_pagealloc_unmap_pages(page, 1 << order); > - > + /* > + * With hardware tag-based KASAN, memory tags must be set > + * before unmapping the page with debug_pagealloc. > + */ > kasan_free_nondeferred_pages(page, order, fpi_flags); Looking at this again, I think we need to move kasan_() callback above arch_free_page(), as that can also make the page unavailable. I'll send v2.
