From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933454Ab2GEXcd (ORCPT ); Thu, 5 Jul 2012 19:32:33 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:35003 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932162Ab2GEXcb (ORCPT ); Thu, 5 Jul 2012 19:32:31 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Glauber Costa Cc: , , Andrew Morton , Tejun Heo , Greg Kroah-Hartman References: <1341496805-26394-1-git-send-email-glommer@parallels.com> Date: Thu, 05 Jul 2012 16:31:57 -0700 In-Reply-To: <1341496805-26394-1-git-send-email-glommer@parallels.com> (Glauber Costa's message of "Thu, 5 Jul 2012 18:00:05 +0400") Message-ID: <8762a1vl76.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=98.207.153.68;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18GPsj0gsLgfLBYqB5KbclCOXZLUUTtEe4= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.1 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0007] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa03 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_XMDrugObfuBody_08 obfuscated drug references X-Spam-DCC: XMission; sa03 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Glauber Costa X-Spam-Relay-Country: Subject: Re: [PATCH] force dentry revalidation after namespace change X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Glauber Costa writes: > When we change the namespace tag of a sysfs entry, the associated dentry > is still kept around. readdir() will work correctly and not display the > old entries, but open() will still succeed, so will reads and writes. > > This will no longer happen if sysfs is remounted, hinting that this is a > cache-related problem. Equalivalently to remounting you can do echo 3 > /proc/sys/vm/drop_caches. > I am using the following sequence to demonstrate that: > > shell1: > ip link add type veth > unshare -nm > > shell2: > ip link set veth1 > cat /sys/devices/virtual/net/veth1/ifindex > > Before that patch, this will succeed (fail to fail). After it, it will > correctly return an error. Differently from a normal rename, which we > handle fine, changing the object namespace will keep it's path intact. > So this check seems necessary as well. Overall good bug spotting, and good spotting of where the fix should live. Your summary should have said: [PATCH] fail dentry revalidation after namespace change And you have the test slightly wrong below. > Signed-off-by: Glauber Costa > CC: Tejun Heo > CC: Eric W. Biederman > CC: Greg Kroah-Hartman > --- > fs/sysfs/dir.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c > index e6bb9b2..c24bdd9 100644 > --- a/fs/sysfs/dir.c > +++ b/fs/sysfs/dir.c > @@ -307,6 +307,7 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd) > { > struct sysfs_dirent *sd; > int is_dir; > + int type; > > if (nd->flags & LOOKUP_RCU) > return -ECHILD; > @@ -314,6 +315,10 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd) > sd = dentry->d_fsdata; > mutex_lock(&sysfs_mutex); > > + type = sysfs_ns_type(sd); > + if (sd->s_ns && (sysfs_info(dentry->d_sb)->ns[type] != sd->s_ns)) > + goto out_bad; > + First this check should be down below with after the other rename checks. Second the test should be: type = KOBJ_NS_TYPE_NONE; if (sd->s_parent) type = sysfs_ns_type(sd->s_parent); if (type && (sysfs_info(dentry->d_sb)->ns[type] != sd->s_ns)) goto out_bad; The important difference there it is the directory that the dirent is in that the type comes from. Not the dirent itself. > /* The sysfs dirent has been deleted */ > if (sd->s_flags & SYSFS_FLAG_REMOVED) > goto out_bad; Glauber. Do you think you can fix your patch and resubmit. Eric