[rlc-10/6.12.0-211.39.1.el10_2] KVM: x86: Check for invalid/obsolete root *after* making MMU pages available - #1508
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…ailable cve CVE-2026-64561 commit-author Sean Christopherson <seanjc@google.com> commit 2abd528 Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages. Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages. Note #2, inheriting role.invalid when creating child shadow pages is also far from ideal; that flaw will be addressed separately. Reported-by: Hyunwoo Kim <imv4bel@gmail.com> Fixes: f95eec9 ("KVM: x86/mmu: Don't put invalid SPs back on the list of active pages") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> (cherry picked from commit 2abd528) Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>
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