From fc62a4e8dee2d1a9037e8cdeaa52ba67457f7300 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 19 Mar 2024 17:15:42 -0700 Subject: [PATCH] KVM: Explicitly disallow activatating a gfn_to_pfn_cache with INVALID_GPA Explicit disallow activating a gfn_to_pfn_cache with an error gpa, i.e. INVALID_GPA, to ensure that KVM doesn't mistake a GPA-based cache for an HVA-based cache (KVM uses INVALID_GPA as a magic value to differentiate between GPA-based and HVA-based caches). WARN if KVM attempts to activate a cache with INVALID_GPA, purely so that new caches need to at least consider what to do with a "bad" GPA, as all existing usage of kvm_gpc_activate() guarantees gpa != INVALID_GPA. I.e. removing the WARN in the future is completely reasonable if doing so would yield cleaner/better code overall. Reviewed-by: David Woodhouse Reviewed-by: Paul Durrant Link: https://lore.kernel.org/r/20240320001542.3203871-4-seanjc@google.com Signed-off-by: Sean Christopherson --- virt/kvm/pfncache.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 91b0e329006b..f618719644e0 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -418,6 +418,13 @@ static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) { + /* + * Explicitly disallow INVALID_GPA so that the magic value can be used + * by KVM to differentiate between GPA-based and HVA-based caches. + */ + if (WARN_ON_ONCE(kvm_is_error_gpa(gpa))) + return -EINVAL; + return __kvm_gpc_activate(gpc, gpa, KVM_HVA_ERR_BAD, len); }