KVM: x86/mmu: Fix struct guest_walker arrays for 5-level paging

BugLink: https://bugs.launchpad.net/bugs/1867194
[ Upstream commit f6ab0107a4942dbf9a5cf0cca3f37e184870a360 ]

Define PT_MAX_FULL_LEVELS as PT64_ROOT_MAX_LEVEL, i.e. 5, to fix shadow
paging for 5-level guest page tables.  PT_MAX_FULL_LEVELS is used to
size the arrays that track guest pages table information, i.e. using a
"max levels" of 4 causes KVM to access garbage beyond the end of an
array when querying state for level 5 entries.  E.g. FNAME(gpte_changed)
will read garbage and most likely return %true for a level 5 entry,
soft-hanging the guest because FNAME(fetch) will restart the guest
instead of creating SPTEs because it thinks the guest PTE has changed.

Note, KVM doesn't yet support 5-level nested EPT, so PT_MAX_FULL_LEVELS
gets to stay "4" for the PTTYPE_EPT case.

Fixes: 855feb673640 ("KVM: MMU: Add 5 level EPT & Shadow page table support.")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 152c2978a2563be65395e16015b0c0edfd970e26..b665452499cb6716f6d4ae00805a6191a0ade100 100644 (file)
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -36,7 +36,7 @@
        #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
        #define PT_HAVE_ACCESSED_DIRTY(mmu) true
        #ifdef CONFIG_X86_64
-       #define PT_MAX_FULL_LEVELS 4
+       #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL
        #define CMPXCHG cmpxchg
        #else
        #define CMPXCHG cmpxchg64