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Date: Tue, 2 Feb 2021 17:57:25 +0100
From: Marco Elver <elver@...gle.com>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Will Deacon <will.deacon@....com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Peter Collingbourne <pcc@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Branislav Rankov <Branislav.Rankov@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/12] kasan: optimize large kmalloc poisoning
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@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
> ---
> 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
>
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