lkml.org 
[lkml]   [2012]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 3/3] pppoatm: protect against freeing of vcc
On Tue, Nov 27, 2012 at 06:02:29PM +0000, David Woodhouse wrote:
> On Tue, 2012-11-27 at 18:39 +0100, Krzysztof Mazur wrote:
> > Yes, I missed that one - it's even worse, I introduced that bug
> > in "[PATCH 1/7] atm: detach protocol before closing vcc". Before that
> > patch that scenario shouldn't happen because vcc was closed before
> > calling pppoatm_send(vcc, NULL) - the driver should provide appropriate
> > synchronization.
> >
> > I think that we should just drop that patch. With later changes it's not
> > necessary - the pppoatm_send() can be safely called while closing vcc.
>
> I'm not running with that patch. This bug exists for br2684 even before
> it, and I think also for pppoatm.
>
> In solos-pci at least, the ops->close() function doesn't flush all
> pending skbs for this vcc before returning. So can be a tasklet
> somewhere which has loaded the address of the vcc->pop function from one
> of them, and is going to call it in some unspecified amount of time.
>
> Should we make the device's ->close function wait for all TX and RX skbs
> for this vcc to complete?

Yes, the ->close() can sleep and after vcc is closed the ->pop() shouldn't be
called.


While reviewing your br2684 patch I also found that some ATM drivers does
not call ->pop() when ->send() fails, they should do:

if (vcc->pop)
vcc->pop(vcc, skb);
else
dev_kfree_skb(skb);

but some drivers just call dev_kfree_skb(skb).

I think that we should add atm_pop() function that does that and fix all
drivers.

Krzysiek


\
 
 \ /
  Last update: 2012-11-27 20:21    [W:0.161 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site