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Mon, 24 Aug 2026 09:03:51 -0700 (PDT) Date: Mon, 24 Aug 2026 18:03:47 +0200 From: =?utf-8?Q?G=C3=BCnther?= Noack To: Justin Suess Cc: =?utf-8?Q?G=C3=BCnther?= Noack , mic@digikod.net, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH v2 0/6] landlock: Add scoped access bit for SysV message queues Message-ID: References: <20260727230833.138165-1-utilityemal77@gmail.com> <20260822.c9dcabf4999f@gnoack.org> <20260822.3340c3dd2a46@gnoack.org> <20260824.abc934a59c55@gnoack.org> 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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Aug 24, 2026 at 08:47:28AM -0400, Justin Suess wrote: > On Mon, Aug 24, 2026 at 08:36:10AM +0200, Günther Noack wrote: > > Agreed. I am personally leaning on the side of closing the gap as > > well, even if it reduces functionality somewhat. SystemV Message > > Queues are used very seldomly (as can be seen in Debian Code Search) > > and it would affect few programs. > > > From msgget(2): > > A new message queue is created if key has the value IPC_PRIVATE or > key isn't IPC_PRIVATE, no message queue with the given key key > exists, and IPC_CREAT is specified in msgflg. > > So more specifically, we will disallow if all three of these are true: > > - IPC_CREAT is specified > - IPC_PRIVATE is not specified. > - The queue referenced by key does not already exist > > Or if these two are true: > > - The queue referenced by key already exists. > - The queue referenced by the key is not part of the scope. > > Effectively, this allows as much as possible, including msgget(2) on an > existing queue within a scope. We technically allow msgget(2) on an existing queue within a scope, but if I understand this correctly, there is now no way to *create* such a queue within the scope. So effectively, that msgget(2) can not succeed, no? I agree with your sentiment that we don't need to implement the allow-listing approach right now. It seems like significant effort for a very small number of use cases. —Günther