From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752992Ab1DUTEg (ORCPT ); Thu, 21 Apr 2011 15:04:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:6186 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752365Ab1DUTEf (ORCPT ); Thu, 21 Apr 2011 15:04:35 -0400 Date: Thu, 21 Apr 2011 21:03:32 +0200 From: Oleg Nesterov To: Matt Fleming , Chris Metcalf Cc: Tejun Heo , linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , "H. Peter Anvin" , Matt Fleming Subject: arch/tile/kernel/hardwall.c:do_hardwall_trap unsafe/wrong usage of ->sighand Message-ID: <20110421190332.GA2570@redhat.com> References: <1302031310-1765-1-git-send-email-matt@console-pimps.org> <1302031310-1765-3-git-send-email-matt@console-pimps.org> <20110413194231.GA15330@redhat.com> <20110414113456.5182a582@mfleming-mobl1.ger.corp.intel.com> <20110414190012.GA23517@redhat.com> <20110416140813.5c90b1fc@mfleming-mobl1.ger.corp.intel.com> <20110418164513.GA25930@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110418164513.GA25930@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/18, Oleg Nesterov wrote: > > On 04/16, Matt Fleming wrote: > > > > 3. I suspect most people find the rules of ->sighand pretty > > confusing. Just look at > > > > arch/tile/kernel/hardwall.c:do_hardwall_trap() > > > > the use of siglock there looks buggy to me. > > Indeed, I agree. It shouldn't use __group_send_sig_info() at all. > I'll send the patch. Nobody outside of signal code should play with > ->sighand, this is almost always wrong. Hmm. It turns out, I can't make the patch because I do not understand what this code tries to do. hardwall_activate() adds the thread to hardwall_list, but do_hardwall_trap() sends the signal to the whole process. I know nothing about arch/tile and probably this is correct, but could you confirm this? Note that SIGILL can be delivered to another thread in the thread-group, is it correct? Also. Is it supposed that SIGILL can have a hanlder or can be blocked, or it should always kill the whole thread group? I think we need the patch below, assuming that SIGILL should be sent to the single thread and it is fine to have a handler for SIGILL. Oleg. --- sigprocmask/arch/tile/kernel/hardwall.c~1_sighand 2011-04-06 21:33:42.000000000 +0200 +++ sigprocmask/arch/tile/kernel/hardwall.c 2011-04-21 20:56:36.000000000 +0200 @@ -268,12 +268,10 @@ void __kprobes do_hardwall_trap(struct p found_processes = 0; list_for_each_entry(p, &rect->task_head, thread.hardwall_list) { BUG_ON(p->thread.hardwall != rect); - if (p->sighand) { + if (!(p->flags & PF_EXITING)) { found_processes = 1; pr_notice("hardwall: killing %d\n", p->pid); - spin_lock(&p->sighand->siglock); - __group_send_sig_info(info.si_signo, &info, p); - spin_unlock(&p->sighand->siglock); + do_send_sig_info(info.si_signo, &info, p, false); } } if (!found_processes)