Re: [PATCH] target: close target_put_sess_cmd() vs. core_tmr_abort_task() race

Greg Kroah-Hartman
2013-03-19T00:26:28Z

On Mon, Mar 18, 2013 at 06:56:57PM -0400, Jörn Engel wrote:
> On Mon, 18 March 2013 17:04:11 -0700, Greg Kroah-Hartman wrote:
> > On Mon, Mar 18, 2013 at 06:28:53PM -0400, Jörn Engel wrote:
> > > It is possible for one thread to to take se_sess->sess_cmd_lock in
> > > core_tmr_abort_task() before taking a reference count on
> > > se_cmd->cmd_kref, while another thread in target_put_sess_cmd() drops
> > > se_cmd->cmd_kref before taking se_sess->sess_cmd_lock.
> > >
> > > This introduces kref_put_and_lock() and uses it in
> > > target_put_sess_cmd() to close the race window.
> >
> > We already have kref_put_mutex(), why not just call this
> > kref_put_spinlock()?
>
> Back when I originally wrote this patch, kref_put_mutex() didn't exist
> yet. So there is my evil predetermined plan to introduce random
> inconsistencies by being consistent with atomic_dec_and_lock()
> instead.

Don't be evil, leave that up to the professionals :)

> If you think this matters I can rename the function and resend.

Please do, it is good to name things correctly, when we have the chance.

greg k-h