netdev - Re: [PATCH net] xfrm: Delete hold

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Message-ID: <20130806080506.GF25511@secunet.com>
Date:	Tue, 6 Aug 2013 10:05:06 +0200
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Fan Du <fan.du@...driver.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net] xfrm: Delete hold_timer when destroy policy

On Fri, Aug 02, 2013 at 09:22:08AM +0800, Fan Du wrote:
> 
> 
> On 2013年08月01日 20:01, Steffen Klassert wrote:
> >On Thu, Aug 01, 2013 at 06:08:36PM +0800, Fan Du wrote:
> >>Both policy timer and hold_timer need to be deleted when destroy policy
> >>Bad mood today, maybe I'm wrong about this...
> >>
> >>Signed-off-by: Fan Du<fan.du@...driver.com>
> >>---
> >>  net/xfrm/xfrm_policy.c |    2 +-
> >>  1 files changed, 1 insertions(+), 1 deletions(-)
> >>
> >>diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> >>index d8da6b8..f7078eb 100644
> >>--- a/net/xfrm/xfrm_policy.c
> >>+++ b/net/xfrm/xfrm_policy.c
> >>@@ -308,7 +308,7 @@ void xfrm_policy_destroy(struct xfrm_policy *policy)
> >>  {
> >>  	BUG_ON(!policy->walk.dead);
> >>
> >>-	if (del_timer(&policy->timer))
> >>+	if (del_timer(&policy->timer) || del_timer(&policy->polq.hold_timer))
> >>  		BUG();
> >>
> >
> >The timers should be already deleted when xfrm_policy_destroy() is
> >called. This is just to check if that really happened and to
> >catch this bug if not. So it's not a bug fix, it just helps to
> >catch a potential bug. I'll consider to take this into ipsec-next
> >after some testing.
> >
> 
> On the contrary, please take a look at callers of xfrm_policy_destroy.
> Code flow is as below:
> 
>   xfrm_policy_alloc() /* setup timer/hold_timer here */ (1)
> 
>   /* do something with this policy, insert or something else */
> 
>   goto err; /* bail out if bad things happens */
> 
>   return ok
> 
> err:
>   xfrm_policy_destroy() /*So both timers in (1) need to be deleted */
> 

setup_timer() does not arm the timer, it just initializes the timer.
So the timer is not pending when xfrm_policy_destroy() is called
on error. The del_timer() in xfrm_policy_destroy() is really just
to catch a bug. That's also the reason why we call BUG() if we
delete a pending timer.

Anyway, applied to ipsec-next.

Thanks!
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