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Mon, 04 Mar 2024 09:56:04 -0800 (PST) Received: from www.outflux.net ([198.0.35.241]) by smtp.gmail.com with ESMTPSA id t7-20020a170902e84700b001d9a91af8a4sm8792261plg.28.2024.03.04.09.56.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Mar 2024 09:56:03 -0800 (PST) Date: Mon, 4 Mar 2024 09:56:03 -0800 From: Kees Cook To: Adrian Ratiu Cc: Christian Brauner , linux-fsdevel@vger.kernel.org, kernel@collabora.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Guenter Roeck , Doug Anderson , Jann Horn , Andrew Morton , Randy Dunlap , Mike Frysinger Subject: Re: [PATCH v2] proc: allow restricting /proc/pid/mem writes Message-ID: <202403040951.C63C3DF5@keescook> References: <20240301213442.198443-1-adrian.ratiu@collabora.com> <20240304-zugute-abtragen-d499556390b3@brauner> <39e47-65e5d100-1-5e37bd0@176022561> <20240304-legten-pelzmantel-1dca3659a892@brauner> <3a1eb-65e5dc00-15-364077c0@216340496> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3a1eb-65e5dc00-15-364077c0@216340496> On Mon, Mar 04, 2024 at 02:35:29PM +0000, Adrian Ratiu wrote: > Yes, easy to block and also respect page permissions (can't write > read-only memory) as well as require ptrace access anyway by checking > PTRACE_MODE_ATTACH_REALCREDS. right, I don't think process_vm_writev() ignores page permissions? i.e. I don't see where it is using FOLL_FORCE, which is one of the central problems with /proc/$pid/mem. (Which reminds me, this is worth mentioning more explicitly in the commit log for v3.) -- Kees Cook