On Wed, Oct 19, 2022 at 10:59:20AM +0000, Huang, Kai wrote:
> static int __sgx_vepc_fault(struct sgx_vepc *vepc,
> struct vm_area_struct *vma, unsigned long addr)
> {
> ......
> /* Calculate index of EPC page in virtual EPC's page_array */
> index = vma->vm_pgoff + PFN_DOWN(addr - vma->vm_start);
>
> epc_page = xa_load(&vepc->page_array, index);
> if (epc_page)
> return 0;
>
> ...
> }
>
> As you can see if the EPC page has already been populated at a given index of
> one virtual EPC instance, the current fault handler just assumes the mapping is
> already there and returns success immediately. This causes a bug when one
> virtual EPC instance is shared by multi processes via fork(): if the EPC page at
> one index is already populated by the parent process, when the child accesses
> the same page using different virtual address, the fault handler just returns
> success w/o actually setting up the mapping for the child, resulting in endless
> page fault.
>
> This needs to be fixed in no matter what way.
I think you mean that vm_insert_pfn() does not happen for child because
of early return? I did not understand the part about "different virtual
addresses", as it is the same mapping.
R, Jarkko
