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From:   "Saleem, Shiraz" <shiraz.saleem@intel.com>
To:     Jason Gunthorpe <jgg@nvidia.com>,
        Lv Yunlong <lyl2019@mail.ustc.edu.cn>
CC:     "Latif, Faisal" <faisal.latif@intel.com>,
        "dledford@redhat.com" <dledford@redhat.com>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] infiniband/i40iw: Fix a use after free in
 i40iw_cm_event_handler
Thread-Topic: [PATCH] infiniband/i40iw: Fix a use after free in
 i40iw_cm_event_handler
Thread-Index: AQHXFiSqLozaSAmrJEO2QxUkby8zNKp/oHYA//+kHnA=
Date:   Fri, 12 Mar 2021 01:13:39 +0000
Message-ID: <1fc386d78c044d3da723fe38446edb75@intel.com>
References: <20210311031414.5011-1-lyl2019@mail.ustc.edu.cn>
 <20210311182114.GA2733907@nvidia.com>
In-Reply-To: <20210311182114.GA2733907@nvidia.com>
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> Subject: Re: [PATCH] infiniband/i40iw: Fix a use after free in
> i40iw_cm_event_handler
> 
> On Wed, Mar 10, 2021 at 07:14:14PM -0800, Lv Yunlong wrote:
> > In the case of I40IW_CM_EVENT_ABORTED, i40iw_event_connect_error()
> > could be called to free the event->cm_node. However, event->cm_node
> > will be used after and cause use after free. It needs to add flags to
> > inform that event->cm_node has been freed.
> >
> > Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> > ---
> >  drivers/infiniband/hw/i40iw/i40iw_cm.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> This might be OK (though I don't like the free variable), Shiraz??
> 

How was this reproduced? Do you have some call trace leading up to use after free?

The cm_node refcnt is bumped at creation time and once in i40iw_receive_ilq before packet is processed.
That should protect the cm_node from disappearing in the event handler in the abort event case.
The dec at end of i40iw_receive ilq should be point where the cm_node is freed specifically in the abort case.

Shiraz