Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751570AbaLZXtG (ORCPT ); Fri, 26 Dec 2014 18:49:06 -0500 Received: from mail-ie0-f177.google.com ([209.85.223.177]:59417 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808AbaLZXtE (ORCPT ); Fri, 26 Dec 2014 18:49:04 -0500 MIME-Version: 1.0 In-Reply-To: <20141226221444.GA13349@amd> References: <20141226221444.GA13349@amd> From: ivo welch Date: Sat, 27 Dec 2014 07:48:42 +0800 X-Google-Sender-Auth: OEK0suMK5V9MwNFp5CmDqTM5UaI Message-ID: Subject: Re: fanotify bug on gdb -- hard crash To: Pavel Machek Cc: linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org hi pavel---I do a complete fresh install on ubuntu 64-bit 14.10 in a vmware virtual machine. the gcc version is 4.9.1. this way I cannot have made a mistake. ;-) the compile is gcc -g -o testfa testfa.c . the gdb and program must run with root privilege. without it, it will just abort on the fd test. then gdb, do "b main", "run", and step through with 'n's. you should see "calling fanotify_mark: fd=3" and then, on the next 'n', it should never return from the fanotify_mark. you should not be able to interrupt. at this point, you have to pull the plug. (I think I also trigger this sometimes without gdb, but then it is not intermittent but replicable. I started debugging because of this issue.) /iaw ---- Ivo Welch (ivo.welch@gmail.com) http://www.ivo-welch.info/ J. Fred Weston Professor of Finance Anderson School at UCLA, C519 Director, UCLA Anderson Fink Center for Finance and Investments Free Finance Textbook, http://book.ivo-welch.info/ Editor, Critical Finance Review, http://www.critical-finance-review.org/ On Sat, Dec 27, 2014 at 6:14 AM, Pavel Machek wrote: > On Fri 2014-12-26 22:45:38, ivo welch wrote: >> I am not a kernel developer, so forgive the intrusion. > > Good bug reports are always welcome. > >> I suspect I have found either a bug in gdb (less likely) or a bug in >> fanotify (more likely). it is replicable, and the code is almost >> unchanged from the example in the fanotify man page. to trigger it, >> all an su needs to do is to step through the program below with gdb >> 7.8.1 'n' command, and linux locks up the system pretty hard (reboot > > Hard lockup -> this can't be gdb problem. > >> required). I have confirmed the replicability of this issue on a >> clean arch 2014.12.01 3.17.6-1 system and on a clean ubuntu 14.10 >> system, both VMs created just to check it. /iaw > > Does it need root priviledges to trigger? > > Best regards, > Pavel > > > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/