CVE-2010-0727 kernel: gfs/gfs2 locking code DoS flaw

[Eugene Teo <eugeneteo () kernel sg>]

static int
gfs_lock(struct file *file, int cmd, struct file_lock *fl)
{
..
        if ((ip->i_di.di_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
                return -ENOLCK;
..
}

This is a check for mandatory locking where the GFS/GFS2 locking code 
will skip the lock in case sgid bits are set for the file. This can be 
triggered to cause a crash on a system mounting a GFS/GFS2 filesystem.

I believe only GFS2 is part of the upstream kernel, and GFS only affects 
Red Hat Enterprise Linux.

https://bugzilla.redhat.com/CVE-2010-0727
http://lkml.org/lkml/2010/3/11/269

Thanks, Eugene