On Mon, Feb 01, 2021 at 08:43PM +0100, Andrey Konovalov wrote:
> Similarly to kasan_kmalloc(), kasan_kmalloc_large() doesn't need
> to unpoison the object as it as already unpoisoned by alloc_pages()
> (or by ksize() for krealloc()).
>
> This patch changes kasan_kmalloc_large() to only poison the redzone.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
> ---
> mm/kasan/common.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 128cb330ca73..a7eb553c8e91 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -494,7 +494,6 @@ EXPORT_SYMBOL(__kasan_kmalloc);
> void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
> gfp_t flags)
> {
> - struct page *page;
> unsigned long redzone_start;
> unsigned long redzone_end;
>
> @@ -504,12 +503,23 @@ void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
> if (unlikely(ptr == NULL))
> return NULL;
>
> - page = virt_to_page(ptr);
> + /*
> + * The object has already been unpoisoned by kasan_alloc_pages() for
> + * alloc_pages() or by ksize() for krealloc().
> + */
> +
> + /*
> + * The redzone has byte-level precision for the generic mode.
> + * Partially poison the last object granule to cover the unaligned
> + * part of the redzone.
> + */
> + if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> + kasan_poison_last_granule(ptr, size);
> +
> + /* Poison the aligned part of the redzone. */
> redzone_start = round_up((unsigned long)(ptr + size),
> KASAN_GRANULE_SIZE);
> - redzone_end = (unsigned long)ptr + page_size(page);
> -
> - kasan_unpoison(ptr, size);
> + redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
> kasan_poison((void *)redzone_start, redzone_end - redzone_start,
> KASAN_PAGE_REDZONE);
>
> --
> 2.30.0.365.g02bc693789-goog
>
