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f28e9c7fce
Fix misleading and arguably wrong comments in the TDP MMU's fast zap flow. The comments, and the fact that actually zapping invalid roots was added separately, strongly suggests that zapping invalid roots is an optimization and not required for correctness. That is a lie. KVM _must_ zap invalid roots before returning from kvm_mmu_zap_all_fast(), because when it's called from kvm_mmu_invalidate_zap_pages_in_memslot(), KVM is relying on it to fully remove all references to the memslot. Once the memslot is gone, KVM's mmu_notifier hooks will be unable to find the stale references as the hva=>gfn translation is done via the memslots. If KVM doesn't immediately zap SPTEs and userspace unmaps a range after deleting a memslot, KVM will fail to zap in response to the mmu_notifier due to not finding a memslot corresponding to the notifier's range, which leads to a variation of use-after-free. The other misleading comment (and code) explicitly states that roots without a reference should be skipped. While that's technically true, it's also extremely misleading as it should be impossible for KVM to encounter a defunct root on the list while holding mmu_lock for write. Opportunistically add a WARN to enforce that invariant. Fixes: |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.