From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DF9227DA73; Tue, 25 Mar 2025 19:45:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742931914; cv=none; b=pcKouYjABC5fKmgKNh7Bq68ygw765u74e8C+T6xzuXdug2VvpxUn6AmUW49E77/H9rIy6eVRxd+p29QKLlkvdWsraP5UCHpf6/etZaE08QXllm7TozvmeK067RINw2O9Ll3j/hPFElj8G+4Nx3ULLxxfwFBPH2JbNj66suDguIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742931914; c=relaxed/simple; bh=xGYquhQCBrhq2OSfhRrStIcjF6AppssofRH9M5AUzbA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fgt5LdyYZd7URFr+FjXasi3BYycBlMd9qRNSitAUkLGHLPWkpFUB+McfsxobEkk5DfuZY0qckPvgWznKfDAgUiZ5AF6YQ7b1Av78UcU/+vU7zK2ndwCyHq6AxVefs7ijlaMVZaGtekcdsx0FSjNdXZolXEY8rUb2Z2e5hx66UJE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e/VzJZYo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="e/VzJZYo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 500A7C4CEE4; Tue, 25 Mar 2025 19:45:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742931913; bh=xGYquhQCBrhq2OSfhRrStIcjF6AppssofRH9M5AUzbA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=e/VzJZYoLKtf+M1/ZFVlJVERgZhOI5sX9iBIKBC19rg5IpwfmNoYHDWxwHFThqoBK u1mMlajcwQx4PH7oOBGSGWPxJ/cA25CuGB8DNvgJ0WRUIrs6CN8k9uXboWPjW3Etbq iwD8gqCU8jMVvqJsbFz3+xoUYScVnJ/l6mQ+u47jD9o/64WdZvWmJ+hH4hZvw43VdC 3esxSCJplc7cVi93uM0qo1Aa1Z9PvEPm+FCVzi5IH3HZbevIRWBLV1hsa44m4T3+qx nPy2bAJtJDry0sbjsks/GARUeVYYfXgxDbVYdH1DJhUOvUkbgQMFB6RhxFuIZhiwY+ d2b9QyO+2nO9w== Date: Tue, 25 Mar 2025 12:45:10 -0700 From: Kees Cook To: "Christoph Lameter (Ampere)" Cc: Vlastimil Babka , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Miguel Ojeda , Nathan Chancellor , Marco Elver , Nick Desaulniers , Przemek Kitszel , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 5/5] [DEBUG] slab: Report number of NULLings Message-ID: <202503251244.CA3E0F8@keescook> References: <20250321202620.work.175-kees@kernel.org> <20250321204105.1898507-5-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Mar 24, 2025 at 09:16:47AM -0700, Christoph Lameter (Ampere) wrote: > On Fri, 21 Mar 2025, Kees Cook wrote: > > > diff --git a/include/linux/slab.h b/include/linux/slab.h > > index 2717ad238fa2..a4740c8b6ccb 100644 > > --- a/include/linux/slab.h > > +++ b/include/linux/slab.h > > @@ -469,6 +469,8 @@ void __kfree(const void *objp); > > void __kfree_sensitive(const void *objp); > > size_t __ksize(const void *objp); > > > > +extern atomic_t count_nulled; > > That is a scalability issue. Use a vmstat counter instead? Yeah, this patch (marked "DEBUG") isn't intended for upstreaming. It was just a quick hack to get a ballpark statistic. :) -- Kees Cook