From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756346Ab2GFJhW (ORCPT ); Fri, 6 Jul 2012 05:37:22 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:50340 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751354Ab2GFJhT (ORCPT ); Fri, 6 Jul 2012 05:37:19 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Glauber Costa Cc: , , Andrew Morton , Greg Thelen , Serge Hallyn , Tejun Heo , Greg Kroah-Hartman References: <1341565747-15374-1-git-send-email-glommer@parallels.com> Date: Fri, 06 Jul 2012 02:37:00 -0700 In-Reply-To: <1341565747-15374-1-git-send-email-glommer@parallels.com> (Glauber Costa's message of "Fri, 6 Jul 2012 13:09:07 +0400") Message-ID: <87hatli62r.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=in01.mta.xmission.com;;;ip=98.207.153.68;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18Dmd6SDR266OoHK8uZVYquWiVbsfRZY+8= 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: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa04 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_XMDrugObfuBody_08 obfuscated drug references X-Spam-DCC: XMission; sa04 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Glauber Costa X-Spam-Relay-Country: Subject: Re: [PATCH v2] fail 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 in01.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. Note reads and writes of file handles open before the move should continue to work. > This will no longer happen if sysfs is remounted, hinting that this is a > cache-related problem. > > 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. > > [ v2: get type from parent, as suggested by Eric Biederman ] Reviewed-by: "Eric W. Biederman" > Signed-off-by: Glauber Costa > CC: Tejun Heo > CC: Eric W. Biederman > CC: Greg Kroah-Hartman > --- > fs/sysfs/dir.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c > index e6bb9b2..c0bf38a 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; > @@ -326,6 +327,13 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd) > if (strcmp(dentry->d_name.name, sd->s_name) != 0) > goto out_bad; > > + /* The sysfs dirent has been moved to a different namespace */ > + 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; > + > mutex_unlock(&sysfs_mutex); > out_valid: > return 1;