linux-kernel - Re: [PATCH] scsi: Let scsi_execute_cmd() mark args->sshdr as invalid

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Message-ID: <191c7661-c47f-5aba-97b9-ff698bda4bc7@acm.org>
Date:   Mon, 22 May 2023 06:31:44 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     John Garry <john.g.garry@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>, stable@...r.kernel.org
Subject: Re: [PATCH] scsi: Let scsi_execute_cmd() mark args->sshdr as invalid

On 5/22/23 02:55, John Garry wrote:
> On 19/05/2023 18:39, Bart Van Assche wrote:
>>        *args->resid = scmd->resid_len;
>> -    if (args->sense)
>> -        memcpy(args->sense, scmd->sense_buffer, SCSI_SENSE_BUFFERSIZE);
>> +    if (args->sense) {
>> +        *args->sense = scmd->sense_buffer;
>> +        scmd->sense_buffer = NULL;
> 
> I think that you will agree that this is not a good pattern to follow. 
> We cannot have SCSI core allocating the sense buffer but a driver 
> freeing it.

Why not? Something similar can happen anywhere in the kernel anywhere 
reference counting is used.

Bart.