linux-kernel - Re: RE: [PATCH] infiniband/i40iw: Fix a use after free in i40iw_cm_event

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Date:   Fri, 12 Mar 2021 09:57:12 +0800 (GMT+08:00)
From:   lyl2019@...l.ustc.edu.cn
To:     "Saleem, Shiraz" <shiraz.saleem@...el.com>
Cc:     "Jason Gunthorpe" <jgg@...dia.com>,
        "Latif, Faisal" <faisal.latif@...el.com>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: RE: [PATCH] infiniband/i40iw: Fix a use after free in
 i40iw_cm_event_handler




> -----原始邮件-----
> 发件人: "Saleem, Shiraz" <shiraz.saleem@...el.com>
> 发送时间: 2021-03-12 09:13:39 (星期五)
> 收件人: "Jason Gunthorpe" <jgg@...dia.com>, "Lv Yunlong" <lyl2019@...l.ustc.edu.cn>
> 抄送: "Latif, Faisal" <faisal.latif@...el.com>, "dledford@...hat.com" <dledford@...hat.com>, "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
> 主题: RE: [PATCH] infiniband/i40iw: Fix a use after free in i40iw_cm_event_handler
> 
> > 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@...l.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
> 

This problem was reported by a path-sensitive analyzer developed by our Security Lab(Loccs).
The analyzer reported that there is a feasible path to free event->cm_node and use it after,
and that is what i described in the first commit.

Thanks.