Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932360Ab3DCHFl (ORCPT ); Wed, 3 Apr 2013 03:05:41 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:60218 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762361Ab3DCHFk (ORCPT ); Wed, 3 Apr 2013 03:05:40 -0400 MIME-Version: 1.0 In-Reply-To: <20130403053534.GA8091@kroah.com> References: <1364957903-10341-1-git-send-email-ming.lei@canonical.com> <20130403030403.GA26913@redhat.com> <20130403053534.GA8091@kroah.com> Date: Wed, 3 Apr 2013 15:05:37 +0800 Message-ID: Subject: Re: [PATCH] sysfs: check if one entry has been removed before freeing From: Ming Lei To: Greg Kroah-Hartman Cc: Dave Jones , linux-kernel@vger.kernel.org, Sasha Levin Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1729 Lines: 43 On Wed, Apr 3, 2013 at 1:35 PM, Greg Kroah-Hartman wrote: > On Wed, Apr 03, 2013 at 11:52:39AM +0800, Ming Lei wrote: >> On Wed, Apr 3, 2013 at 11:04 AM, Dave Jones wrote: >> > On Wed, Apr 03, 2013 at 10:58:23AM +0800, Ming Lei wrote: >> > >> > > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c >> > > index 1bf016b..328ef9b 100644 >> > > --- a/fs/sysfs/dir.c >> > > +++ b/fs/sysfs/dir.c >> > > @@ -268,6 +268,13 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) >> > > */ >> > > parent_sd = sd->s_parent; >> > > >> > > + if (unlikely(!(sd->s_flags & SYSFS_FLAG_REMOVED))) { >> > > + printk(KERN_ERR "sysfs: free using entry: %s/%s\n", >> > > + parent_sd ? parent_sd->s_name : "", >> > > + sd->s_name); >> > > + BUG(); >> > > + } >> > >> > Please use WARN instead of BUG. For an in-ram filesystem like >> > sysfs, there's no real reason to lock-up the machine in this way >> > making it harder to debug. >> >> If WARN is used, the freed memory will be allocated to other >> kernel components, then sysfs may change the memory and cause >> destruction, so maybe it is better to use BUG to stop kernel. > > No, it's never ok to call BUG(), sorry, please fix this. Sorry, could you explain it in a bit detail? IMO, it is really a bug when code runs here, and there are much similar BUG_ON() uses in current sysfs code too. Thanks, -- Ming Lei -- 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/