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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id fs12sm77488pjb.49.2021.01.11.10.33.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Jan 2021 10:33:39 -0800 (PST) Date: Mon, 11 Jan 2021 10:33:38 -0800 From: Kees Cook To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, jannh@google.com, jeffv@google.com, minchan@kernel.org, mhocko@suse.com, shakeelb@google.com, rientjes@google.com, edgararriaga@google.com, timmurray@google.com, linux-mm@kvack.org, selinux@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v2 1/1] mm/madvise: replace ptrace attach requirement for process_madvise Message-ID: <202101111033.2D03EA97@keescook> References: <20210111170622.2613577-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210111170622.2613577-1-surenb@google.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.009234, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jan 11, 2021 at 09:06:22AM -0800, Suren Baghdasaryan wrote: > process_madvise currently requires ptrace attach capability. > PTRACE_MODE_ATTACH gives one process complete control over another > process. It effectively removes the security boundary between the > two processes (in one direction). Granting ptrace attach capability > even to a system process is considered dangerous since it creates an > attack surface. This severely limits the usage of this API. > The operations process_madvise can perform do not affect the correctness > of the operation of the target process; they only affect where the data > is physically located (and therefore, how fast it can be accessed). > What we want is the ability for one process to influence another process > in order to optimize performance across the entire system while leaving > the security boundary intact. > Replace PTRACE_MODE_ATTACH with a combination of PTRACE_MODE_READ > and CAP_SYS_NICE. PTRACE_MODE_READ to prevent leaking ASLR metadata > and CAP_SYS_NICE for influencing process performance. > > Signed-off-by: Suren Baghdasaryan Reviewed-by: Kees Cook -- Kees Cook