Re: [PATCH v6 2/7] fpga: sec-mgr: enable secure updates

From: Russ Weight <russell.h.weight@intel.com>
To: "Martin Hundebøll" <mhu@silicom.dk>,
	mdf@kernel.org, linux-fpga@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: trix@redhat.com, lgoncalv@redhat.com, yilun.xu@intel.com,
	hao.wu@intel.com, matthew.gerlach@intel.com
Subject: Re: [PATCH v6 2/7] fpga: sec-mgr: enable secure updates
Date: Tue, 1 Dec 2020 15:30:38 -0800	[thread overview]
Message-ID: <25ee1ab1-3d81-d9b9-240d-143a9936d0f8@intel.com> (raw)
In-Reply-To: <5b49ef38-2c03-02bc-6a1e-5b663180acf3@silicom.dk>

On 12/1/20 12:47 AM, Martin Hundebøll wrote:
> Hi Russ,
>
> On 01/12/2020 00.54, Russ Weight wrote:
>> Thanks Martin. I'll work on a fix for this.
>
> Attached is my in-house fix.
>
> // Martin
>
>> On 11/26/20 6:02 AM, Martin Hundebøll wrote:
>>> Hi Russ,
>>>
>>> I found another thing while testing this...
>>>
>>> On 06/11/2020 02.09, Russ Weight wrote:
>>>
>>> <snip>
>>>
>>>> +static ssize_t filename_store(struct device *dev, struct device_attribute *attr,
>>>> +                  const char *buf, size_t count)
>>>> +{
>>>> +    struct fpga_sec_mgr *smgr = to_sec_mgr(dev);
>>>> +    int ret = count;
>>>> +
>>>> +    if (count == 0 || count >= PATH_MAX)
>>>> +        return -EINVAL;
>>>> +
>>>> +    mutex_lock(&smgr->lock);
>>>> +    if (smgr->driver_unload || smgr->progress != FPGA_SEC_PROG_IDLE) {
>>>> +        ret = -EBUSY;
>>>> +        goto unlock_exit;
>>>> +    }
>>>> +
>>>> +    smgr->filename = kstrndup(buf, count - 1, GFP_KERNEL);
>>>
>>> The `count - 1` is meant to remove a trailing newline, but opae-sdk writes the filename without newline, so better do it conditionally...

After looking at how kstrndup() is used elsewhere, and after
doing some experimentation, I think the best fix may be to just
remove the "- 1":

    smgr->filename = kstrndup(buf, count, GFP_KERNEL);

The code shouldn't have assumed a "\n", and I don't think the
kernel should be required to do white-space cleanup.

Does this fix seem OK to you?

- Russ
>>>
>>>> +    if (!smgr->filename) {
>>>> +        ret = -ENOMEM;
>>>> +        goto unlock_exit;
>>>> +    }
>>>> +
>>>> +    smgr->err_code = FPGA_SEC_ERR_NONE;
>>>> +    smgr->progress = FPGA_SEC_PROG_READING;
>>>> +    reinit_completion(&smgr->update_done);
>>>> +    schedule_work(&smgr->work);
>>>> +
>>>> +unlock_exit:
>>>> +    mutex_unlock(&smgr->lock);
>>>> +    return ret;
>>>> +}
>>>> +static DEVICE_ATTR_WO(filename);
>>>> +
>>>> +static struct attribute *sec_mgr_update_attrs[] = {
>>>> +    &dev_attr_filename.attr,
>>>> +    NULL,
>>>> +};
>>>
>>> Thanks,
>>> Martin
>>