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Authentication-Results: mx.google.com; spf=pass (google.com: domain of miles.chen@mediatek.com designates 210.61.82.184 as permitted sender) smtp.mailfrom=miles.chen@mediatek.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=mediatek.com X-UUID: 725620696fd34fab965989687eb53529-20190809 X-UUID: 725620696fd34fab965989687eb53529-20190809 Received: from mtkexhb01.mediatek.inc [(172.21.101.102)] by mailgw02.mediatek.com (envelope-from ) (Cellopoint E-mail Firewall v4.1.10 Build 0707 with TLS) with ESMTP id 735304464; Fri, 09 Aug 2019 22:11:58 +0800 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs07n1.mediatek.inc (172.21.101.16) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Fri, 9 Aug 2019 22:11:58 +0800 Received: from [172.21.77.33] (172.21.77.33) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Fri, 9 Aug 2019 22:11:58 +0800 Message-ID: <1565359918.12824.20.camel@mtkswgap22> Subject: Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages From: Miles Chen To: Matthew Wilcox CC: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , , , , , "Tobin C . Harding" , Kees Cook Date: Fri, 9 Aug 2019 22:11:58 +0800 In-Reply-To: <20190809024644.GL5482@bombadil.infradead.org> References: <20190809010837.24166-1-miles.chen@mediatek.com> <20190809024644.GL5482@bombadil.infradead.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N X-Bogosity: Ham, tests=bogofilter, spamicity=0.001192, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 2019-08-08 at 19:46 -0700, Matthew Wilcox wrote: > On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@mediatek.com wrote: > > Possible approaches are: > > 1. stop printing kernel addresses > > 2. print with %pK, > > 3. print with %px. > > No. The point of obscuring kernel addresses is that if the attacker manages to find a way to get the kernel to spit out some debug messages that we shouldn't > leak all this extra information. got it. > > > 4. do nothing > > 5. Find something more useful to print. agree > > > INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____) > > ... you don't have any randomness on your platform? We have randomized base on our platforms. > But if you have randomness, at least some of these "pointers" are valuable > because you can compare them against "pointers" printed by other parts > of the kernel. Understood. Keep current %p, do not leak kernel addresses. I'll collect more cases and see if we really need some extra information. (maybe the @offset in current message is enough) thanks for your comments!