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Fri, 17 Jul 2020 09:20:16 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B7450300446; Fri, 17 Jul 2020 11:20:14 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A22FF29CF6F51; Fri, 17 Jul 2020 11:20:14 +0200 (CEST) Date: Fri, 17 Jul 2020 11:20:14 +0200 From: Peter Zijlstra To: ira.weiny@intel.com Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , x86@kernel.org, Dave Hansen , Dan Williams , Vishal Verma , Andrew Morton , Fenghua Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH RFC V2 12/17] memremap: Add zone device access protection Message-ID: <20200717092014.GB10769@hirez.programming.kicks-ass.net> References: <20200717072056.73134-1-ira.weiny@intel.com> <20200717072056.73134-13-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200717072056.73134-13-ira.weiny@intel.com> X-Rspamd-Queue-Id: B9D181802D544 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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, Jul 17, 2020 at 12:20:51AM -0700, ira.weiny@intel.com wrote: > From: Ira Weiny > > Device managed memory exposes itself to the kernel direct map which > allows stray pointers to access these device memories. > > Stray pointers to normal memory may result in a crash or other > undesirable behavior which, while unfortunate, are usually recoverable > with a reboot. Stray writes to areas such as non-volatile memory are > permanent in nature and thus are more likely to result in permanent user > data loss vs a stray write to other memory areas > + pks_update_protection(dev_page_pkey, PKEY_DISABLE_ACCESS); So on the one hand you talk about the problem of stray writes, but then you disable all access.