Quoting Andrew Morton ([email protected]): > On Fri, 6 Jul 2012 13:09:07 +0400 > Glauber Costa <[email protected]> wrote: > > > 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. > > > > 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. > > > > ... > > > > --- 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)) > > eww, the code is assuming that KOBJ_NS_TYPE_NONE has a value of zero. > Don't do that; it smells bad. > > I renamed my version of this patch to "sysfs: fail dentry revalidation > after namespace change", as carefully explained in section 15 of the > excellent Documentation/SubmittingPatches, then queued this: > > > From: Andrew Morton <[email protected]> > Subject: sysfs-fail-dentry-revalidation-after-namespace-change-fix > > don't assume that KOBJ_NS_TYPE_NONE==0. Also save a test-n-branch. > > Cc: Eric W. Biederman <[email protected]> > Cc: Glauber Costa <[email protected]> > Cc: Greg Kroah-Hartman <[email protected]> > Cc: Tejun Heo <[email protected]>
Acked-by: Serge E. Hallyn <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > --- > > fs/sysfs/dir.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff -puN > fs/sysfs/dir.c~sysfs-fail-dentry-revalidation-after-namespace-change-fix > fs/sysfs/dir.c > --- a/fs/sysfs/dir.c~sysfs-fail-dentry-revalidation-after-namespace-change-fix > +++ a/fs/sysfs/dir.c > @@ -329,10 +329,12 @@ static int sysfs_dentry_revalidate(struc > > /* The sysfs dirent has been moved to a different namespace */ > type = KOBJ_NS_TYPE_NONE; > - if (sd->s_parent) > + 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; > + if (type != KOBJ_NS_TYPE_NONE && > + sysfs_info(dentry->d_sb)->ns[type] != sd->s_ns) > + goto out_bad; > + } > > mutex_unlock(&sysfs_mutex); > out_valid: > _ > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
