On Sun, 2025-05-11 at 09:03 +0100, David Hildenbrand wrote:
>>> return -ENODEV;
>>> +
>>> + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) !=
>>> + (VM_SHARED | VM_MAYSHARE)) {
>>> + return -EINVAL;
>>> + }
>>> +
>>> + vm_flags_set(vma, VM_DONTDUMP);
>>
>> Hi Fuad,
>>
>> Sorry if I missed this, but why exactly do we set VM_DONTDUMP here?
>> Could you leave a small comment? (I see that it seems to have
>> originally come from Patrick? [1]) I get that guest memory VMAs
>> generally should have VM_DONTDUMP; is there a bigger reason?
Iirc, I essentially copied my mmap handler from secretmem for that RFC. But
even for direct map removal, it seems this is not needed, because get_dump_page
goes via GUP, which errors out for direct map removed VMAs. So what David is
saying below also applies in that case.
> (David replying)
>
> I assume because we might have inaccessible parts in there that SIGBUS
> on access.
>
> get_dump_page() does ignore any errors, though (returning NULL), so
> likely we don't need VM_DONTDUMP.
>
> --
> Cheers,
>
> David / dhildenb
Best,
Patrick
