From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750849AbdEEQ0s (ORCPT ); Fri, 5 May 2017 12:26:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53954 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750713AbdEEQ0r (ORCPT ); Fri, 5 May 2017 12:26:47 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 77E2A4AEA8 Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=oleg@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 77E2A4AEA8 Date: Fri, 5 May 2017 18:26:07 +0200 From: Oleg Nesterov To: Jamie Iles Cc: linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] signal: don't remove SIGNAL_UNKILLABLE for traced tasks. Message-ID: <20170505162606.GA32256@redhat.com> References: <20170504125136.11352-1-jamie.iles@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170504125136.11352-1-jamie.iles@oracle.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 05 May 2017 16:26:46 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jamie, I am sorry for being slow... yes, probably we should start with this simple change, and perhaps we do not really need anything else. But let me think about this till Monday, perhaps we can remove this "clear SIGNAL_UNKILLABLE" logic in force_sig_info() altogether. On 05/04, Jamie Iles wrote: > > When forcing a signal, SIGNAL_UNKILLABLE is removed to prevent recursive > faults, but this is undesirable when tracing. For example, debugging an > init process (whether global or namespace), hitting a breakpoint and > SIGTRAP will force SIGTRAP and then remove SIGNAL_UNKILLABLE. > Everything continues fine, but then once debugging has finished, the > init process is left killable which is unlikely what the user expects, > resulting in either an accidentally killed init or an init that stops > reaping zombies. > > Cc: Andrew Morton > Cc: Oleg Nesterov > Signed-off-by: Jamie Iles > --- > kernel/signal.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/signal.c b/kernel/signal.c > index 7e59ebc2c25e..5516a0cda668 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1185,7 +1185,11 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t) > recalc_sigpending_and_wake(t); > } > } > - if (action->sa.sa_handler == SIG_DFL) > + /* > + * Don't clear SIGNAL_UNKILLABLE for traced tasks, users won't expect > + * debugging to leave init killable. > + */ > + if (action->sa.sa_handler == SIG_DFL && !t->ptrace) > t->signal->flags &= ~SIGNAL_UNKILLABLE; > ret = specific_send_sig_info(sig, info, t); > spin_unlock_irqrestore(&t->sighand->siglock, flags); > -- > 2.12.0.rc0 >