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Date:   Mon, 1 Nov 2021 20:06:38 -0700
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Subject: Re: [PATCH] scsi: core: initialize cmd->cmnd before it is used
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To:     dgilbert@interlog.com, Tadeusz Struk <tadeusz.struk@linaro.org>,
        linux-scsi@vger.kernel.org
Cc:     Christoph Hellwig <hch@lst.de>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        syzbot+5516b30f5401d4dcbcae@syzkaller.appspotmail.com
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From:   Bart Van Assche <bvanassche@acm.org>
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On 11/1/21 18:56, Douglas Gilbert wrote:
> On 2021-11-01 4:20 p.m., Bart Van Assche wrote:
>> One of the functions in the call stack in the first message of this email
>> thread is sg_io(). I am not aware of any documentation that specifies 
>> whether
>> it is valid to set cmd_len in the sg_io header to zero. My opinion is 
>> that
>> the SG_IO implementation should either reject cmd_len == 0 or set cmd_len
>> to a valid value if it is zero.
> 
> For the sg driver in production, the v3 interface users (including
> ioctl(<sg_fd>, SG_IO,) ) have this check:
> 
>         if ((!hp->cmdp) || (hp->cmd_len < 6) || (hp->cmd_len > sizeof 
> (cmnd))) {
>                  sg_remove_request(sfp, srp);
>                  return -EMSGSIZE;
>          }

Hi Doug,

Thanks for having taken a look. I found the above check in 
sg_new_write(). To me that function seems to come from a code path that 
is unrelated to sg_io(), the function shown in the call stack in the 
email at the start of this thread. Maybe I overlooked something but I 
haven't found a minimum size check for hdr->cmd_len in sg_io() before 
the blk_execute_rq() call. Should such a check perhaps be added?

Thanks,

Bart.