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Biederman) To: Oleg Nesterov Cc: Jim Newsome , Andrew Morton , Christian Brauner , linux-kernel@vger.kernel.org References: <20210309203919.15920-1-jnewsome@torproject.org> <20210311150820.GA15552@redhat.com> Date: Thu, 11 Mar 2021 10:37:27 -0600 In-Reply-To: <20210311150820.GA15552@redhat.com> (Oleg Nesterov's message of "Thu, 11 Mar 2021 16:08:21 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lKOJP-0031iH-0U;;;mid=;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18DeM/j9n2X2ms1qI2KqEBrWyWfZAhqUGo= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa07.xmission.com X-Spam-Level: ** X-Spam-Status: No, score=2.0 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,TR_Symld_Words,T_TM2_M_HEADER_IN_MSG, T_TooManySym_01,T_TooManySym_02,XMSubLong autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4939] * 1.5 TR_Symld_Words too many words that have symbols inside * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **;Oleg Nesterov X-Spam-Relay-Country: X-Spam-Timing: total 308 ms - load_scoreonly_sql: 0.07 (0.0%), signal_user_changed: 11 (3.7%), b_tie_ro: 10 (3.1%), parse: 1.40 (0.5%), extract_message_metadata: 23 (7.4%), get_uri_detail_list: 1.57 (0.5%), tests_pri_-1000: 22 (7.3%), tests_pri_-950: 1.88 (0.6%), tests_pri_-900: 1.01 (0.3%), tests_pri_-90: 65 (21.1%), check_bayes: 63 (20.6%), b_tokenize: 5 (1.6%), b_tok_get_all: 6 (1.9%), b_comp_prob: 1.81 (0.6%), b_tok_touch_all: 47 (15.3%), b_finish: 0.96 (0.3%), tests_pri_0: 167 (54.4%), check_dkim_signature: 0.66 (0.2%), check_dkim_adsp: 2.2 (0.7%), poll_dns_idle: 0.49 (0.2%), tests_pri_10: 2.1 (0.7%), tests_pri_500: 8 (2.5%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH v3] do_wait: make PIDTYPE_PID case O(1) instead of O(n) X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov writes: > On 03/10, Eric W. Biederman wrote: >> >> Jim Newsome writes: >> >> > +static int do_wait_pid(struct wait_opts *wo) >> > +{ >> > + struct task_struct *target = pid_task(wo->wo_pid, PIDTYPE_PID); >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >> This is subtle change in behavior. >> >> Today on the task->children list we only place thread group leaders. > > Aaah, yes, thanks Eric! > >> So the code either needs a thread_group_leader filter on target before >> the ptrace=0 case or we need to use "pid_task(wo->wo_pid, PIDTYPE_TGID)" >> and "pid_task(wo->wo_pid, PIDTYPE_PID)" for the "ptrace=1" case. > > Agreed, > >> I would like to make thread_group_leaders go away > > Hmm, why? Mostly because we have class of very nasty bugs to fix because code thinks one thread is special. There has been and I think still is code that mishandles zombie thread group leaders. Particularly nasty are zombie thread group leaders after userspace has called setresuid in a way that changes signal permissions. Eric