From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + ptrace-fix-ptrace_listen-race-corrupting-task-state.patch added to -mm tree Date: Tue, 04 Apr 2017 14:57:10 -0700 Message-ID: <58e416b6.BIb/JkkYa7mr6HzL%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33732 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753834AbdDDV5L (ORCPT ); Tue, 4 Apr 2017 17:57:11 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: bsegall@google.com, mm-commits@vger.kernel.org The patch titled Subject: ptrace: fix PTRACE_LISTEN race corrupting task->state has been added to the -mm tree. Its filename is ptrace-fix-ptrace_listen-race-corrupting-task-state.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/ptrace-fix-ptrace_listen-race-corrupting-task-state.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/ptrace-fix-ptrace_listen-race-corrupting-task-state.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: bsegall@google.com Subject: ptrace: fix PTRACE_LISTEN race corrupting task->state In PT_SEIZED + LISTEN mode STOP/CONT signals cause a wakeup against __TASK_TRACED. If this races with the ptrace_unfreeze_traced at the end of a PTRACE_LISTEN, this can wake the task /after/ the check against __TASK_TRACED, but before the reset of state to TASK_TRACED. This causes it to instead clobber TASK_WAKING, allowing a subsequent wakeup against TRACED while the task is still on the rq wake_list, corrupting it. Link: http://lkml.kernel.org/r/xm26y3vfhmkp.fsf_-_@bsegall-linux.mtv.corp.google.com Signed-off-by: Ben Segall --- v2: slight clarification in comments, put the conditional around the whole wakeup area Oleg mentioned a preference for making LISTEN unfreeze instead; I have no preference there, just wanted to make sure that this doesn't get forgotten entirely. 1 file changed, 10 insertions(+), 4 deletions(-) index 0af928712174..7cc49c3e73af 100644 Signed-off-by: Andrew Morton --- kernel/ptrace.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff -puN kernel/ptrace.c~ptrace-fix-ptrace_listen-race-corrupting-task-state kernel/ptrace.c --- a/kernel/ptrace.c~ptrace-fix-ptrace_listen-race-corrupting-task-state +++ a/kernel/ptrace.c @@ -184,11 +184,17 @@ static void ptrace_unfreeze_traced(struc WARN_ON(!task->ptrace || task->parent != current); + /* + * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up + * remotely. Recheck state under the lock to close this race. + */ spin_lock_irq(&task->sighand->siglock); - if (__fatal_signal_pending(task)) - wake_up_state(task, __TASK_TRACED); - else - task->state = TASK_TRACED; + if (task->state == __TASK_TRACED) { + if (__fatal_signal_pending(task)) + wake_up_state(task, __TASK_TRACED); + else + task->state = TASK_TRACED; + } spin_unlock_irq(&task->sighand->siglock); } _ Patches currently in -mm which might be from bsegall@google.com are ptrace-fix-ptrace_listen-race-corrupting-task-state.patch