linux-kernel - Re: [PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr

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Message-ID: <826bb7b5-c7ea-db24-878e-a2997a1cd9a6@oracle.com>
Date:   Wed, 30 Jun 2021 20:13:59 -0500
From:   michael.christie@...cle.com
To:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Cc:     subbu.seetharaman@...adcom.com, ketan.mukadam@...adcom.com,
        jitendra.bhivare@...adcom.com, jejb@...ux.ibm.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr_ip

On 6/29/21 5:02 PM, Martin K. Petersen wrote:
> 
> Lv,
> 
>> In the free_cmd error path of callee beiscsi_exec_nemb_cmd(),
>> nonemb_cmd->va is freed by dma_free_coherent().  As req =
>> nonemb_cmd.va, we can see that the freed nonemb_cmd.va is still
>> dereferenced and used by req->ip_params.ip_record.status.
> 
>> My patch uses status to replace req->ip_params.ip_record.status to
>> avoid the uaf.
> 
> This status is captured prior to executing the command so it doesn't
> actually reflect whether the operation was successful (which I believe
> was the intent).
> 
> Some of the callers of beiscsi_exec_nemb_cmd() pass a response buffer
> and a response length as the two last arguments. Since
> beiscsi_exec_nemb_cmd() frees the command before returning, passing a
> response buffer seems to be the only way to get meaningful data out.
> 
> I am not sure whether the OPCODE_COMMON_ISCSI_NTWK_MODIFY_IP_ADDR
> operation returns something useful from the controller. As far as I can
> tell not all operations have a response buffer defined.
> 
> My recommendation would be to add a response buffer and try to decipher
> what comes back from the firmware. Also, beiscsi_if_set_ip() appears to
> have the same problem as beiscsi_if_clr_ip().
> 

Hopefully the broadcom devs will chime in, but it doesn't look like we get
a response buffer. I think we just need to move the:

      dma_free_coherent(&ctrl->pdev->dev, nonemb_cmd->size,
                          nonemb_cmd->va, nonemb_cmd->dma);

to a helper and have the callers free the cmd.

Oh yeah, I guess we haven't been able to hit this bug, because
beiscsi_if_set_ip/beiscsi_if_clr_ip hasn't been run since 2013.
This patch
https://patchwork.kernel.org/project/linux-scsi/patch/20210701002559.89533-1-michael.christie@oracle.com/
allows us to be able to set the IP and hit those code paths.