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

[JÃrn Engel]

On Mon, 18 March 2013 17:04:11 -0700, Greg Kroah-Hartman wrote:
> On Mon, Mar 18, 2013 at 06:28:53PM -0400, JÃrn 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.

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

JÃrn

--
Computer system analysis is like child-rearing; you can do grievous damage,
but you cannot ensure success."
-- Tom DeMarco
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