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[88.114.211.119]) by smtp.gmail.com with ESMTPSA id n26sm3300666lfq.120.2020.10.05.02.03.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Oct 2020 02:03:30 -0700 (PDT) Subject: Re: [PATCH] mm: optionally disable brk() To: Michal Hocko Cc: David Hildenbrand , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20201002171921.3053-1-toiwoton@gmail.com> <653873ef-2a57-37e0-1ac3-fba763652b35@redhat.com> <2a0f5ade-d770-c36e-50bc-ff0c8e9dacbf@gmail.com> <20201005061248.GN4555@dhcp22.suse.cz> <7d7b1ac5-d6a7-5e43-8fb8-12b844d7f501@gmail.com> <20201005082239.GQ4555@dhcp22.suse.cz> From: Topi Miettinen Message-ID: <4f0b1f0e-ab26-cd4e-607c-2c5b9933f10a@gmail.com> Date: Mon, 5 Oct 2020 12:03:27 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201005082239.GQ4555@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5.10.2020 11.22, Michal Hocko wrote: > On Mon 05-10-20 11:11:35, Topi Miettinen wrote: > [...] >> I think hardened, security oriented systems should disable brk() completely >> because it will increase the randomization of the process address space >> (ASLR). This wouldn't be a good option to enable for systems where maximum >> compatibility with legacy software is more important than any hardening. > > I believe we already do have means to filter syscalls from userspace for > security hardened environements. Or is there any reason to duplicate > that and control during the configuration time? This is true, but seccomp can't be used for cases where NoNewPrivileges can't be enabled (setuid/setgid binaries present which sadly is still often the case even in otherwise hardened system), so it's typically not possible to install a filter for the whole system. -Topi