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Date: Fri, 06 Jul 2012 02:37:00 -0700 From: ebiederm@...ssion.com (Eric W. Biederman) To: Glauber Costa <glommer@...allels.com> Cc: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Greg Thelen <gthelen@...gle.com>, Serge Hallyn <serge.hallyn@...onical.com>, Tejun Heo <tj@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: Re: [PATCH v2] fail dentry revalidation after namespace change Glauber Costa <glommer@...allels.com> 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 <pid_of_shell_1> > 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" <ebiederm@...ssion.com> > Signed-off-by: Glauber Costa <glommer@...allels.com> > CC: Tejun Heo <tj@...nel.org> > CC: Eric W. Biederman <ebiederm@...ssion.com> > CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org> > --- > 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; -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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