[WIP] fix(vmm): Do not store UFFD handle in VMM #5341
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## feature/secret-hiding #5341 +/- ##
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- Coverage 81.96% 81.91% -0.06%
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Files 250 250
Lines 27570 27571 +1
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- Hits 22599 22584 -15
- Misses 4971 4987 +16
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This is to unregister all UFFD ranges when the UFFD handler is disconnected so that no further UFFD message is sent if the handler is not longer available.
The test verifies that if the fault-all handler exits, the VM is still functional. THe test is mostly relevant to Secret Free VMs. Signed-off-by: Nikita Kalyazin <[email protected]>
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We can't do that for functional and security reasons, see the comment for |
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Changes
Do not store UFFD handle in VMM. The UFFD object gets dropped as soon as the last reference to it (in the handler) goes away.
Reason
This is required to make sure no further UFFD messages will be sent to the handler that is no longer available to avoid an infinite lockup.
This is relevant for Secret Free VMs, because the UFFD handler uses
writeinstead ofUFFDIO_COPYto prepopulate guest memory and is not required to preinstall userspace page tables while doing it.License Acceptance
By submitting this pull request, I confirm that my contribution is made under
the terms of the Apache 2.0 license. For more information on following Developer
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CONTRIBUTING.md.PR Checklist
[ ] I have runtools/devtool checkbuild --allto verify that the PR passesbuild checks on all supported architectures.
tools/devtool checkstyleto verify that the PR passes theautomated style checks.
how they are solving the problem in a clear and encompassing way.
[ ] I have updated any relevant documentation (both in code and in the docs)in the PR.
[ ] I have mentioned all user-facing changes inCHANGELOG.md.[ ] If a specific issue led to this PR, this PR closes the issue.[ ] When making API changes, I have followed theRunbook for Firecracker API changes.
[ ] I have tested all new and changed functionalities in unit tests and/orintegration tests.
[ ] I have linked an issue to every newTODO.rust-vmm.