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[140.211.169.12]) by mx.google.com with ESMTPS id d15si14451235pgt.498.2019.01.28.10.20.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 10:20:57 -0800 (PST) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 1228223DD; Mon, 28 Jan 2019 18:20:57 +0000 (UTC) Date: Mon, 28 Jan 2019 10:20:55 -0800 From: Andrew Morton To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , kernel-hardening@lists.openwall.com, Kees Cook , Michael Ellerman Subject: Re: [PATCH] mm: Prevent mapping slab pages to userspace Message-Id: <20190128102055.5b0790549542891c4dca47a3@linux-foundation.org> In-Reply-To: <20190125173827.2658-1-willy@infradead.org> References: <20190125173827.2658-1-willy@infradead.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 25 Jan 2019 09:38:27 -0800 Matthew Wilcox wrote: > It's never appropriate to map a page allocated by SLAB into userspace. > A buggy device driver might try this, or an attacker might be able to > find a way to make it happen. It wouldn't surprise me if someone somewhere is doing this. Rather than mysteriously breaking their code, how about we emit a warning and still permit it to proceed, for a while?