Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753421AbaBOPdv (ORCPT ); Sat, 15 Feb 2014 10:33:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:19508 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753357AbaBOPdu (ORCPT ); Sat, 15 Feb 2014 10:33:50 -0500 Date: Sat, 15 Feb 2014 16:33:41 +0100 From: Oleg Nesterov To: Al Viro Cc: Linus Torvalds , Dave Chinner , Dave Jones , Eric Sandeen , Linux Kernel , xfs@oss.sgi.com Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled. Message-ID: <20140215153341.GA18472@redhat.com> References: <20140212113928.GO18016@ZenIV.linux.org.uk> <20140212211421.GP18016@ZenIV.linux.org.uk> <20140213174020.GA14455@redhat.com> <20140215052531.GX18016@ZenIV.linux.org.uk> <20140215142700.GA15540@redhat.com> <20140215152251.GY18016@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140215152251.GY18016@ZenIV.linux.org.uk> 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 02/15, Al Viro wrote: > > On Sat, Feb 15, 2014 at 03:27:00PM +0100, Oleg Nesterov wrote: > > > 1. info->q can be already freed if SIGQUEUE_PREALLOC. > > > > Once get_signal_to_deliver() or any other caller drops ->siglock > > another thread can do sys_timer_delete()->sigqueue_free(). > > How the devil would it find the sucker? It simply frees the SIGQUEUE_PREALLOC sigqueue, k_itimer->sigq. > It's off the list already. Exactly, list_empty(q->list) == T. So release_posix_timer()->sigqueue_free() assumes we can safely free it. > > 2. We need to move do_schedule_next_timer() from dequeue_signal() > > here. > > > > Otherwise ->q can be reused/overwritten by the next send_sigqueue() > > right affter ->siglock is dropped. > > Ditto. We rip them out of queue on collect_signal(); Yes, and dequeue_signal()->do_schedule_next_timer() can trigger another send_sigqueue() which uses the same SIGQUEUE_PREALLOC sigqueue once we drop ->siglock. This is not that bad, but at least ->si_overrun can be overwritten before __setup_rt_frame()->copy_siginfo_to_user(). Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/