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

[Martin Hundebøll]

Hi Russ,

On 02/12/2020 00.30, Russ Weight wrote:
> 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?

Since we always use opae-sdk to write the filename, we wouldn't even notice.

While your'e at it, kerneldoc in mm/util.c suggests to use kmemdup_nul() 
when the size is known.

// Martin