linux-kernel - Re: [PATCH v2] block: fix ioc leak in put_io

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Date:	Tue, 13 Mar 2012 15:47:49 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Xiaotian Feng <xtfeng@...il.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, axboe@...nel.dk,
	linux-kernel@...r.kernel.org, Xiaotian Feng <dannyfeng@...cent.com>
Subject: Re: [PATCH v2] block: fix ioc leak in put_io_context

On Wed, Mar 14, 2012 at 06:44:22AM +0800, Xiaotian Feng wrote:
> On Tue, Mar 13, 2012 at 11:49 PM, Tejun Heo <tj@...nel.org> wrote:
> > On Tue, Mar 13, 2012 at 10:28:20AM -0400, Vivek Goyal wrote:
> >> On Tue, Mar 13, 2012 at 01:21:06PM -0400, Xiaotian Feng wrote:
> >> > diff --git a/block/blk-ioc.c b/block/blk-ioc.c
> >> > index 8b782a6..9690f27 100644
> >> > --- a/block/blk-ioc.c
> >> > +++ b/block/blk-ioc.c
> >> > @@ -145,6 +145,7 @@ static void ioc_release_fn(struct work_struct *work)
> >> >  void put_io_context(struct io_context *ioc)
> >> >  {
> >> >     unsigned long flags;
> >> > +   bool free_ioc = false;
> >> >
> >> >     if (ioc == NULL)
> >> >             return;
> >> > @@ -159,8 +160,13 @@ void put_io_context(struct io_context *ioc)
> >> >             spin_lock_irqsave(&ioc->lock, flags);
> >> >             if (!hlist_empty(&ioc->icq_list))
> >> >                     schedule_work(&ioc->release_work);
> >> > +           else
> >> > +                   free_ioc = true;
> >
> > Calling kmem_cache_free() here directly is probably better.
> 
> I did this on my first try, but I got a kernel warning with the
> following spin_unlock on ioc->lock :(
> We'll hit a use after free bug then...

Ah, you're right.  Thanks.

-- 
tejun
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