[PATCH v4 13/23] KVM: WARN if KVM attempts to do guest-related uaccess with "wrong" process

[Sean Christopherson <seanjc@google.com>]

Now that memslots are torn down before kvm_arch_destroy_vm(), i.e. now that
the massive, unaudited path that is known to have at least one rogue access
to guest memory should be short-circuited before attempting to access user
memory, WARN if KVM attempts to do a user access to guest memory with the
wrong address space.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 include/linux/kvm_host.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index be27b4e8f12d..f3f59bdf7e18 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1355,7 +1355,7 @@ int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 
 static __always_inline __must_check bool kvm_can_do_uaccess(struct kvm *kvm)
 {
-	return current->mm == kvm->mm;
+	return !WARN_ON_ONCE(current->mm != kvm->mm);
 }
 
 #define BUILD_KVM_COPY_USER_WRAPPER(fn, to_user, from_user)				\
-- 
2.56.0.385.gac671c819a-goog