From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 57291 invoked by alias); 28 Oct 2015 18:06:25 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 57282 invoked by uid 89); 28 Oct 2015 18:06:25 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.7 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 28 Oct 2015 18:06:20 +0000 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id B0BD119CBA9; Wed, 28 Oct 2015 18:06:18 +0000 (UTC) Received: from tranklukator.brq.redhat.com (dhcp-1-102.brq.redhat.com [10.34.1.102]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id t9SI6DQe025413; Wed, 28 Oct 2015 14:06:14 -0400 Received: by tranklukator.brq.redhat.com (nbSMTP-1.00) for uid 500 oleg@redhat.com; Wed, 28 Oct 2015 20:02:40 +0100 (CET) Date: Wed, 28 Oct 2015 18:06:00 -0000 From: Oleg Nesterov To: Pedro Alves Cc: Denys Vlasenko , Denys Vlasenko , Andrew Morton , Dmitry Vyukov , Alexander Potapenko , Eric Dumazet , Jan Kratochvil , Julien Tinnes , Kees Cook , Kostya Serebryany , Linus Torvalds , "Michael Kerrisk (man-pages)" , Robert Swiecki , Roland McGrath , syzkaller@googlegroups.com, Linux Kernel Mailing List , "gdb@sourceware.org" Subject: Re: [PATCH 1/2] wait/ptrace: always assume __WALL if the child is traced Message-ID: <20151028190235.GA31914@redhat.com> References: <20151020171754.GA29304@redhat.com> <20151020153155.e03f4219da4014efe6f810b0@linux-foundation.org> <5627EE9E.8040600@redhat.com> <5627F607.4050506@redhat.com> <20151021214703.GA1810@redhat.com> <20151025155440.GB2043@redhat.com> <562E17D8.4000108@redhat.com> <20151028161152.GA24042@redhat.com> <5630ED16.50900@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5630ED16.50900@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-SW-Source: 2015-10/txt/msg00110.txt.bz2 On 10/28, Pedro Alves wrote: > > On 10/28/2015 04:11 PM, Oleg Nesterov wrote: > > On 10/26, Pedro Alves wrote: > >> > >> (Also, in the original test case, if the child gets/raises a signal or execs > >> before exiting, the bash/init/whatever process won't be issuing PTRACE_CONT, > >> and the child will thus end up stuck (though should be SIGKILLable, > > > > Oh, but if it is killable everything is fine. How does this differ from the > > case when, say, you jusr reparent to init and do kill(getpid(), SIGSTOP) ? > > The difference is that if the child called PTRACE_TRACEME, then it goes > to ptrace-stop instead and no amount of SIGCONT unstucks it -- the only way > out is force killing. I agree it's not a major issue as there's a way out > (and thus made it a parens), but I wouldn't call it nice either. IOW, the difference is that it is TASK_TRACED, not TASK_STOPPED. I agree, this is not nice. But this is not nice simply because PTRACE_TRACEME is not nice. > >> All this because PTRACE_TRACEME is broken by design > > > > Heh. I agree. But we can't fix it now. > > Perhaps the man page could document it as deprecated, suggesting > PTRACE_ATTACH/PTRACE_SEIZE instead? I don't know. but I won't mind if you mark PTRACE_ATTACH as deprecated too ;) PTRACE_SEIZE can be used instead and it doesn't abuse SIGSTOP. Oleg.