Messages in this thread | | | Date | Sun, 19 Jun 2022 23:32:07 -0700 | From | Christoph Hellwig <> | Subject | Re: [RFT][PATCH v1 5/6] vfio/ccw: Add kmap_local_page() for memcpy |
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On Sun, Jun 19, 2022 at 11:57:26PM -0300, Jason Gunthorpe wrote: > The remark about io memory is because on s390 memcpy() will crash even > on ioremapped memory, you have to use the memcpy_to/fromio() which > uses the special s390 io access instructions.
Yes. The same is true for various other architectures, inluding arm64 under the right circumstances.
> This helps because we now block io memory from ever getting into these > call paths. I'm pretty sure this is a serious security bug, but would > let the IBM folks remark as I don't know it all that well..
Prevent as in crash when trying to convert it to a page?
> As for the kmap, I thought it was standard practice even if it is a > non-highmem? Aren't people trying to use this for other security > stuff these days?
Ira has been lookin into the protection keys, although they don't apply to s390. Either way I don't object to using kmap, but the commit log doesn't make much sense to me.
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