linux-kernel - Re: [PATCH] RDMA/cma: Fix listener leak in rdma_cma_listen_on

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Message-ID: <20210916135712.GA327412@nvidia.com>
Date:   Thu, 16 Sep 2021 10:57:12 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Tao Liu <thomas.liu@...oud.cn>, dledford@...hat.com,
        haakon.bugge@...cle.com, shayd@...dia.com, avihaih@...dia.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        thomas.liu@...oud.com
Subject: Re: [PATCH] RDMA/cma: Fix listener leak in rdma_cma_listen_on_all()
 failure

On Wed, Sep 15, 2021 at 02:17:56AM +0300, Leon Romanovsky wrote:

> > +static void cma_cancel_listens(struct rdma_id_private *id_priv)
> > +{
> > +	/*
> > +	 * During _destroy_id() it is not possible for this value to transition
> > +	 * from empty to !empty, test it outside to lock to avoid taking a
> > +	 * global lock on every destroy. Only listen all cases will have
> > +	 * something to do
> > +	 */
> > +	if (list_empty(&id_priv->list))
> > +		return;
> 
> IMHO, it is better do not do such check outside of the lock without real
> gain. It is too subtle to rely on _destroy_id() behaviour.

This arrangement would have solved the syzkaller bugs that are
triggering due to the other logic in _destroy_id() being too subtle
already :\

But it can't be done because priv->list is a total mess

Jason