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 16014 invoked from network); 16 Aug 2020 17:11:53 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 16 Aug 2020 17:11:53 -0000 Received: (qmail 3589 invoked by uid 550); 16 Aug 2020 17:11:50 -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 3571 invoked from network); 16 Aug 2020 17:11:50 -0000 From: Florian Weimer To: Rich Felker Cc: musl@lists.openwall.com References: <20200814214136.GP3265@brightrain.aerifal.cx> <20200816035759.GW3265@brightrain.aerifal.cx> <87h7t3j6r6.fsf@mid.deneb.enyo.de> <20200816165642.GZ3265@brightrain.aerifal.cx> Date: Sun, 16 Aug 2020 19:11:37 +0200 In-Reply-To: <20200816165642.GZ3265@brightrain.aerifal.cx> (Rich Felker's message of "Sun, 16 Aug 2020 12:56:42 -0400") Message-ID: <87eeo6ikhi.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [musl] Restrictions on child context after multithreaded fork * Rich Felker: > On Sun, Aug 16, 2020 at 11:10:37AM +0200, Florian Weimer wrote: >> * Rich Felker: >> >> > On some inspection, glibc does not actually attempt to make the child >> > environment unrestricted. The only things it does around fork are: >> >> I think pthread_once initializers that have partially executed are >> also executed from the start in the child if initialization is >> requested again. > > I don't follow how pthread_once is related. The vast majority of the > things I found glibc doing no specific handling for are actual mutable > state not just on-demand initialization. If a fork happens during a pthread_once initialization, the subsystem related to that becomes unavailable after fork. The pthread_once_t reinitialization logic intends to avoid that. Like resetting locks after fork in the new process, it is rather questionable.