From: Jason Gunthorpe jgg@nvidia.com Sent: Monday, July 31, 2023 9:19 PM
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.
Sure. Actually, there are some description as below in patch [1]. Would add some as well here.
"Cache invalidation path is performance path, so it's better to avoid memory allocation in such path. To achieve it, this path reuses the ucmd_buffer to copy user data. So the new data structures are added in the ucmd_buffer union to avoid overflow."
[1] https://lore.kernel.org/linux-iommu/20230724111335.107427-8-yi.l.liu@intel.c...
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.
Ok. so if any mistake on the data structure, the allocation fails in the first place.
Regards, Yi Liu