From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754326Ab1GHRQz (ORCPT ); Fri, 8 Jul 2011 13:16:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20840 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752013Ab1GHRQx (ORCPT ); Fri, 8 Jul 2011 13:16:53 -0400 Date: Fri, 8 Jul 2011 19:14:17 +0200 From: Oleg Nesterov To: Tejun Heo , Linus Torvalds Cc: vda.linux@googlemail.com, jan.kratochvil@redhat.com, pedro@codesourcery.com, indan@nul.nu, bdonlan@gmail.com, linux-kernel@vger.kernel.org Subject: [RFC PATCH 3/3] ptrace: dont send SIGSTOP on auto-attach if PT_SEIZED Message-ID: <20110708171417.GD26943@redhat.com> References: <20110708171320.GA26943@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110708171320.GA26943@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 The fake SIGSTOP during attach has numerous problems. PTRACE_SEIZE is already fine, but we have basically the same problems is SIGSTOP is sent on auto-attach, the tracer can't know if this signal signal should be cancelled or not. Change ptrace_event() to set JOBCTL_TRAP_STOP if the new child is PT_SEIZED, this triggers the PTRACE_EVENT_STOP report. Thereafter a PT_SEIZED task can never report the bogus SIGSTOP. Test-case: #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 #define PTRACE_EVENT_STOP 7 #define WEVENT(s) ((s & 0xFF0000) >> 16) int main(void) { int child, grand_child, status; long message; child = fork(); if (!child) { kill(getpid(), SIGSTOP); fork(); assert(0); return 0x23; } assert(ptrace(PTRACE_SEIZE, child, 0,PTRACE_SEIZE_DEVEL) == 0); assert(wait(&status) == child); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP); assert(ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACEFORK) == 0); assert(ptrace(PTRACE_CONT, child, 0,0) == 0); assert(waitpid(child, &status, 0) == child); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP); assert(WEVENT(status) == PTRACE_EVENT_FORK); assert(ptrace(PTRACE_GETEVENTMSG, child, 0, &message) == 0); grand_child = message; assert(waitpid(grand_child, &status, 0) == grand_child); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP); assert(WEVENT(status) == PTRACE_EVENT_STOP); kill(child, SIGKILL); kill(grand_child, SIGKILL); return 0; } Signed-off-by: Oleg Nesterov --- include/linux/ptrace.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- ptrace/include/linux/ptrace.h~5_clone_no_stop_if_seized 2011-07-08 18:32:05.000000000 +0200 +++ ptrace/include/linux/ptrace.h 2011-07-08 18:32:53.000000000 +0200 @@ -228,7 +228,11 @@ static inline void ptrace_init_task(stru child->ptrace = current->ptrace; __ptrace_link(child, current->parent); - sigaddset(&child->pending.signal, SIGSTOP); + if (child->ptrace & PT_SEIZED) + task_set_jobctl_pending(child, JOBCTL_TRAP_STOP); + else + sigaddset(&child->pending.signal, SIGSTOP); + set_tsk_thread_flag(child, TIF_SIGPENDING); } }