Explicitly check that tdp_iter_start() is handed a valid shadow page
to harden KVM against bugs where
Opportunistically stop the TDP MMU iteration instead of continuing on
with garbage if the incoming root is bogus. Attempting to walk a garbage
root is more likely to caused major problems than doing nothing.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_iter.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c
index d2eb0d4f8710..bd30ebfb2f2c 100644
--- a/arch/x86/kvm/mmu/tdp_iter.c
+++ b/arch/x86/kvm/mmu/tdp_iter.c
@@ -39,13 +39,14 @@ void tdp_iter_restart(struct tdp_iter *iter)
void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root,
int min_level, gfn_t next_last_level_gfn)
{
- int root_level = root->role.level;
-
- WARN_ON(root_level < 1);
- WARN_ON(root_level > PT64_ROOT_MAX_LEVEL);
+ if (WARN_ON_ONCE(!root || (root->role.level < 1) ||
+ (root->role.level > PT64_ROOT_MAX_LEVEL))) {
+ iter->valid = false;
+ return;
+ }
iter->next_last_level_gfn = next_last_level_gfn;
- iter->root_level = root_level;
+ iter->root_level = root->role.level;
iter->min_level = min_level;
iter->pt_path[iter->root_level - 1] = (tdp_ptep_t)root->spt;
iter->as_id = kvm_mmu_page_as_id(root);
--
2.41.0.487.g6d72f3e995-goog
