linux-kernel - Re: [RFC PATCH] RDMA/srp: Fix use-after-free in srp_exit_cmd

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Message-ID: <20220624234757.GD4147@nvidia.com>
Date:   Fri, 24 Jun 2022 20:47:57 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Li Zhijian <lizhijian@...itsu.com>,
        Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] RDMA/srp: Fix use-after-free in srp_exit_cmd_priv

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

> Is calling get_device() and put_device() on the struct ib_device an
> acceptable way to fix this? 

As I said, I don't understand at all how this works. get_device() does
not prevent srp_remove_one() from being called.

Jason