From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 23593 invoked from network); 15 Oct 2020 15:43:42 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 15 Oct 2020 15:43:42 -0000 Received: (qmail 21739 invoked by uid 550); 15 Oct 2020 15:43:36 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 21718 invoked from network); 15 Oct 2020 15:43:35 -0000 Date: Thu, 15 Oct 2020 11:43:23 -0400 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20201015154323.GT17637@brightrain.aerifal.cx> References: <948f6fc6f3458f18152c0f8b505beec0@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <948f6fc6f3458f18152c0f8b505beec0@ispras.ru> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] Why is setrlimit() considered to have per-thread effect? On Thu, Oct 15, 2020 at 08:01:00AM +0300, Alexey Izbyshev wrote: > Hello, > > Commit 544ee752cd[1] claims that setrlimit() is per-thread on Linux, > similarly to setxid() calls, so it should be called via > __synccall(). But this appears to be wrong: the kernel code operates > on tsk->signal[2], which is a per-thread-group structure. Glibc > doesn't call setrlimit() for each thread either. Am I missing > something? POSIX specifies that it sets the limits for the process. If the kernel doesn't do that, we have to implement in userspace. > Tangentially, setgroups() is not called via __synccall(), though it > does have per-thread effect. Is this intentional? POSIX doesn't define setgroups, so it's up to the implementation. Conceptually since POSIX has supplemental groups they probably *should* be forced process-global, so maybe we should change this. For an example that's more clear-cut, setfs[ug]id is explicitly not process-global because it's not a security boundary and the whole purpose is to be able to do local id changes then revert them for the sake of performing access as a different user/group. Rich