On Mon, Jul 31, 2023 at 10:19:09AM -0300, Jason Gunthorpe wrote:
> On Mon, Jul 31, 2023 at 10:07:32AM +0000, Liu, Yi L wrote:
> > > > + goto out_put_hwpt;
> > > > + }
> > > > +
> > > > + /*
> > > > + * Copy the needed fields before reusing the ucmd buffer, this
> > > > + * avoids memory allocation in this path.
> > > > + */
> > > > + user_ptr = cmd->data_uptr;
> > > > + user_data_len = cmd->data_len;
> > >
> > > Uhh, who checks that klen < the temporary stack struct?
> >
> > Take vtd as an example. The invalidate structure is struct iommu_hwpt_vtd_s1_invalidate[1].
> > The klen is sizeof(struct iommu_hwpt_vtd_s1_invalidate)[2]. iommu_hwpt_vtd_s1_invalidate
> > is also placed in the temporary stack struct (actually it is a union)[1]. So the klen should
> > be <= temporary stack.
>
> Ohh, I think I would add a few comments noting that the invalidate
> structs need to be added to that union. Easy to miss.
Added here:
- * Copy the needed fields before reusing the ucmd buffer, this
- * avoids memory allocation in this path.
+ * Copy the needed fields before reusing the ucmd buffer, this avoids
+ * memory allocation in this path. Again, user invalidate data struct
+ * must be added to the union ucmd_buffer.
> > It's not so explicit though. Perhaps worth to have a check like below in this patch?
> >
> > if (unlikely(klen > sizeof(union ucmd_buffer)))
> > return -EINVAL;
>
> Yes, stick this in the domain allocate path with a WARN_ON. The driver
> is broken to allocate a domain with an invalid size.
And here too with a WARN_ON_ONCE.
+ /*
+ * Either the driver is broken by having an invalid size, or the user
+ * invalidate data struct used by the driver is missing in the union.
+ */
+ if (WARN_ON_ONCE(hwpt->domain->ops->cache_invalidate_user &&
+ (!hwpt->domain->ops->cache_invalidate_user_data_len ||
+ hwpt->domain->ops->cache_invalidate_user_data_len >
+ sizeof(union ucmd_buffer)))) {
+ rc = -EINVAL;
+ goto out_abort;
+
+ }
Though I am making this cache_invalidate_user optional here, I
wonder if there actually could be a case that a user-managed
domain doesn't need a cache_invalidate_user op...
Thanks
Nicolin
