linux-kernel - Re: use-after-free in srpt_enable

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Message-ID: <18afff6f-ce0a-1d98-aeb9-236878692e6b@acm.org>
Date:   Sat, 2 Jul 2022 15:26:33 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Mike Christie <michael.christie@...cle.com>,
        "lizhijian@...itsu.com" <lizhijian@...itsu.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: use-after-free in srpt_enable_tpg()

On 6/30/22 18:59, Hillf Danton wrote:
> That hang can be skipped by removing the wait loop in
> srpt_release_sport() - in the direction of 9b64f7d0bb0a, sdev will not
> go home if any sport's refcount does not drop on ground. To do that, add
> port refcount to sdev in the diff below in bid to resurrect 9b64f7d0bb0a.
> 
> Then gc work can be added for dying sports to drop tpg after delaying a second.

I'm afraid that the patch from your email will lead to a use-after-free 
of sdev->pd. As long as a session is live the ch->qp pointer may be 
dereferenced. The sdev->pd pointer is stored in the pd member of struct 
ib_qp and hence may be dereferenced by any function that uses ch->qp.

Thanks,

Bart.