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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id r4sm922290pgp.53.2020.03.26.00.21.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 00:21:31 -0700 (PDT) Date: Thu, 26 Mar 2020 00:21:30 -0700 From: Kees Cook To: Michal Hocko Cc: "Eric W. Biederman" , Vlastimil Babka , Luis Chamberlain , Iurii Zaikin , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org, Ivan Teterevkov , David Rientjes , Matthew Wilcox , "Guilherme G . Piccoli" Subject: Re: [RFC v2 1/2] kernel/sysctl: support setting sysctl parameters from kernel command line Message-ID: <202003260018.81648AA67@keescook> References: <20200325120345.12946-1-vbabka@suse.cz> <874kuc5b5z.fsf@x220.int.ebiederm.org> <20200326065829.GC27965@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200326065829.GC27965@dhcp22.suse.cz> 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 Thu, Mar 26, 2020 at 07:58:29AM +0100, Michal Hocko wrote: > On Wed 25-03-20 17:20:40, Eric W. Biederman wrote: > > Vlastimil Babka writes: > [...] > > > + if (strncmp(param, "sysctl.", sizeof("sysctl.") - 1)) > > > + return 0; > > > > Is there any way we can use a slash separated path. I know > > in practice there are not any sysctl names that don't have > > a '.' in them but why should we artifically limit ourselves? > > Because this is the normal userspace interface? Why should it be any > different from calling sysctl? Right. The common method from userspace is dot-separated (which I agree is weird, but it's been like this for ages: see manpages sysctl(8) and sysctl.conf(5) for the details and examples). While "/" is accepted by sysctl, the files shipped in /etc/sysctl.d/ are all using "." separators. -- Kees Cook