On Fri, 28 Aug 2015, Nathan Lynch wrote:
> On 08/28/2015 05:31 AM, Lee Jones wrote:
> > +static ssize_t rproc_state_write(struct file *filp, const char __user *userbuf,
> > + size_t count, loff_t *ppos)
> > +{
> > + struct rproc *rproc = filp->private_data;
> > + char buf[2];
> > + int ret;
> > +
> > + ret = copy_from_user(buf, userbuf, 1);
> > + if (ret)
> > + return -EFAULT;
> > +
> > + switch (buf[0]) {
> > + case '0':
> > + rproc_shutdown(rproc);
> > + break;
> > + case '1':
> > + ret = rproc_boot(rproc);
> > + if (ret)
> > + dev_warn(&rproc->dev, "Boot failed: %d\n", ret);
> > + break;
> > + default:
> > + dev_err(&rproc->dev, "Unrecognised option: %x\n", buf[1]);
> > + return -EINVAL;
>
> This prints uninitialized kernel stack contents instead of what was
> copied from user space.
Yes, you're right. I will conduct a better test of the failure path
here.
> Is the dev_err statement really necessary anyway?
Yes. As I described in my other mail, this interface is for Kernel
Engineers, who read the kernel log.
> > + }
> > +
> > + return count;
> > +}
>
> If rproc_boot fails, that should be reflected in the syscall result.
>
> This interface is essentially exposing the remoteproc->power refcount to
> user space; is that okay? Seems like it makes it easy to underflow
> remoteproc->power through successive shutdown calls.
If the subsystem is suseptable to underruns someone should think about
adding protection against imbalances in the 'core'.
> The other debugfs interface in remoteproc that has a write method
> (recovery) accepts more expressive string commands as opposed to 0/1.
> It would be more consistent for this interface to take commands such as
> "boot" and "shutdown" IMO.
Agreed.
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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