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[192.55.54.38]) by smtp.gmail.com with ESMTPSA id 203-v6sm6340963pgb.14.2018.08.29.04.49.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Aug 2018 04:49:44 -0700 (PDT) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id 1AE1E3001A3; Wed, 29 Aug 2018 14:49:40 +0300 (+03) Date: Wed, 29 Aug 2018 14:49:40 +0300 From: "Kirill A. Shutemov" To: Baoquan He Cc: tglx@linutronix.de, mingo@kernel.org, hpa@zytor.com, thgarnie@google.com, kirill.shutemov@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] x86/mm/KASLR: Fix the wrong calculation of kalsr region initial size Message-ID: <20180829114940.k36272hhxa7fznva@kshutemo-mobl1> References: <20180829021754.21850-1-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180829021754.21850-1-bhe@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 29, 2018 at 10:17:53AM +0800, Baoquan He wrote: > In memory KASLR, __PHYSICAL_MASK_SHIFT is taken to calculate the > initial size of the direct mapping region. This is right in the > old code where __PHYSICAL_MASK_SHIFT was equal to MAX_PHYSMEM_BITS, > 46bit, and only 4-level mode was supported. > > Later, in commit: > b83ce5ee91471d ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52"), > __PHYSICAL_MASK_SHIFT was changed to be 52 always, no matter it's > 5-level or 4-level. This is wrong for 4-level paging. Then when > adapt phyiscal memory region size based on available memory, it > will overflow if the amount of system RAM and the padding is bigger > than 64TB. > > In fact, here MAX_PHYSMEM_BITS should be used instead. Fix it by > by replacing __PHYSICAL_MASK_SHIFT with MAX_PHYSMEM_BITS. > > Signed-off-by: Baoquan He Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov