linux-kernel - Re: [PATCH v2 13/20] kasan: simplify kasan_poison

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Date:   Wed, 11 Nov 2020 19:42:46 +0100
From:   Marco Elver <elver@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 13/20] kasan: simplify kasan_poison_kfree

On Tue, Nov 10, 2020 at 11:20PM +0100, Andrey Konovalov wrote:
> kasan_poison_kfree() is currently only called for mempool allocations
> that are backed by either kmem_cache_alloc() or kmalloc(). Therefore, the
> page passed to kasan_poison_kfree() is always PageSlab() and there's no
> need to do the check. Remove it.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
> Link: https://linux-review.googlesource.com/id/If31f88726745da8744c6bea96fb32584e6c2778c
> ---
>  mm/kasan/common.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)

Reviewed-by: Marco Elver <elver@...gle.com>

> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 385863eaec2c..819403548f2e 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -432,16 +432,7 @@ void __kasan_poison_kfree(void *ptr, unsigned long ip)
>  	struct page *page;
>  
>  	page = virt_to_head_page(ptr);
> -
> -	if (unlikely(!PageSlab(page))) {
> -		if (ptr != page_address(page)) {
> -			kasan_report_invalid_free(ptr, ip);
> -			return;
> -		}
> -		kasan_poison_memory(ptr, page_size(page), KASAN_FREE_PAGE);
> -	} else {
> -		____kasan_slab_free(page->slab_cache, ptr, ip, false);
> -	}
> +	____kasan_slab_free(page->slab_cache, ptr, ip, false);
>  }
>  
>  void __kasan_kfree_large(void *ptr, unsigned long ip)
> -- 
> 2.29.2.222.g5d2a92d10f8-goog
>