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Mon, 19 Nov 2018 12:55:29 -0800 (PST) Date: Mon, 19 Nov 2018 21:55:20 +0100 From: Christian Brauner To: Aleksa Sarai Cc: ebiederm@xmission.com, linux-kernel@vger.kernel.org, serge@hallyn.com, jannh@google.com, luto@kernel.org, akpm@linux-foundation.org, oleg@redhat.com, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, dancol@google.com, timmurray@google.com, linux-man@vger.kernel.org, Kees Cook Subject: Re: [PATCH v1 2/2] signal: add procfd_signal() syscall Message-ID: <20181119205518.btew3vxwgva4w3zh@brauner.io> References: <20181119103241.5229-1-christian@brauner.io> <20181119103241.5229-3-christian@brauner.io> <20181119202857.k5zw742xjfrw677j@yavin> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20181119202857.k5zw742xjfrw677j@yavin> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 20, 2018 at 07:28:57AM +1100, Aleksa Sarai wrote: > On 2018-11-19, Christian Brauner wrote: > > + if (info) { > > + ret = __copy_siginfo_from_user(sig, &kinfo, info); > > + if (unlikely(ret)) > > + goto err; > > + /* > > + * Not even root can pretend to send signals from the kernel. > > + * Nor can they impersonate a kill()/tgkill(), which adds > > + * source info. > > + */ > > + ret = -EPERM; > > + if ((kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL) && > > + (task_pid(current) != pid)) > > + goto err; > > + } else { > > + prepare_kill_siginfo(sig, &kinfo); > > + } > > I wonder whether we should also have a pidns restriction here, since > currently it isn't possible for a container process using a pidns to > signal processes outside its pidns. AFAICS, this isn't done through an > explicit check -- it's a side-effect of processes in a pidns not being > able to address non-descendant-pidns processes. > > But maybe it's reasonable to allow sending a procfd to a different pidns > and the same operations working on it? If we extend the procfd API to No, I don't think so. I really don't want any fancy semantics in here. Fancy doesn't get merged and fancy is hard to maintain. So we should do something like: if (proc_pid_ns() != current_pid_ns) return EINVAL > allow process creation this would allow a container to create a process > outside its pidns. > > -- > Aleksa Sarai > Senior Software Engineer (Containers) > SUSE Linux GmbH >