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[88.114.222.21]) by smtp.gmail.com with ESMTPSA id s22sm260505lfi.187.2020.12.09.11.08.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Dec 2020 11:08:25 -0800 (PST) Subject: Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations To: Mike Rapoport Cc: linux-hardening@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Jann Horn , Kees Cook , Linux API , Matthew Wilcox References: <20201201214547.9721-1-toiwoton@gmail.com> <9d34fb0a-7aba-1e84-6426-006ea7c3d9f5@gmail.com> <20201203065801.GH751215@kernel.org> From: Topi Miettinen Message-ID: <26f0c73a-3a81-4ba6-2b6f-c5ca73ea866b@gmail.com> Date: Wed, 9 Dec 2020 21:08:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: <20201203065801.GH751215@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US 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 3.12.2020 8.58, Mike Rapoport wrote: > On Wed, Dec 02, 2020 at 08:49:06PM +0200, Topi Miettinen wrote: >> On 1.12.2020 23.45, Topi Miettinen wrote: >>> Memory mappings inside kernel allocated with vmalloc() are in >>> predictable order and packed tightly toward the low addresses. With >>> new kernel boot parameter 'randomize_vmalloc=1', the entire area is >>> used randomly to make the allocations less predictable and harder to >>> guess for attackers. >>> >> >> This also seems to randomize module addresses. I was going to check that >> next, so nice surprise! > > Heh, that's because module_alloc() uses vmalloc() in that way or another :) The modules are still allocated from their small (1.5GB) separate area instead of the much larger (32TB/12.5PB) vmalloc area, which would greatly improve ASLR for the modules. To fix that, I tried to to #define MODULES_VADDR to VMALLOC_START etc. like x86_32 does, but then kernel dies very early without even any output. -Topi