Messages in this thread | | | From | (Eric W. Biederman) | Date | Fri, 06 Jul 2012 02:37:00 -0700 | Subject | Re: [PATCH v2] fail dentry revalidation after namespace change |
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Glauber Costa <glommer@parallels.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@xmission.com>
> Signed-off-by: Glauber Costa <glommer@parallels.com> > CC: Tejun Heo <tj@kernel.org> > CC: Eric W. Biederman <ebiederm@xmission.com> > CC: Greg Kroah-Hartman <gregkh@linuxfoundation.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;
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