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Message-ID: <0d6ffcec-285a-37f8-5f2f-6a16e3631b92@acm.org>
Date:   Fri, 24 Jun 2022 16:57:47 -0700
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Subject: Re: [RFC PATCH] RDMA/srp: Fix use-after-free in srp_exit_cmd_priv
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To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Li Zhijian <lizhijian@fujitsu.com>,
        Leon Romanovsky <leon@kernel.org>, linux-rdma@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220624040253.1420844-1-lizhijian@fujitsu.com>
 <20220624225908.GA303931@nvidia.com>
 <5a4a42fe-c5c8-63fe-365f-e6c74a279cc2@acm.org>
 <20220624234757.GD4147@nvidia.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <20220624234757.GD4147@nvidia.com>
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On 6/24/22 16:47, Jason Gunthorpe wrote:
> On Fri, Jun 24, 2022 at 04:26:06PM -0700, Bart Van Assche wrote:
>> On 6/24/22 15:59, Jason Gunthorpe wrote:
>>> I don't even understand how get_device() prevents this call chain??
>>>
>>> It looks to me like the problem is srp_remove_one() is not waiting for
>>> or canceling some outstanding work.
>>
>> Hi Jason,
>>
>> My conclusions from the call traces in Li's email are as follows:
>> * scsi_host_dev_release() can get called after srp_remove_one().
>> * srp_exit_cmd_priv() uses the ib_device pointer. If srp_remove_one() is
>> called before srp_exit_cmd_priv() then a use-after-free is triggered.
> 
> Shouldn't srp_remove_one() wait for the scsi_host_dev to complete
> destruction? Clearly it cannot continue to exist once the IB device
> has been removed

That sounds like an interesting approach to me. Li, do you perhaps want 
to implement this approach?

Thanks,

Bart.