[PATCH 07/24] KVM: SEV: WARN if KVM attempts to setup scratch area with min_len==0

[Paolo Bonzini]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

Now that all paths in KVM properly validate the length needed for the
scratch area, and are guaranteed to pass in a non-zero length, WARN if KVM
attempts to configured the scratch area with min_len==0 to guard against
future bugs.

Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Reviewed-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-ID: <20260501202250.2115252-8-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 6072fecfe994..a3e85348ace9 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3669,6 +3669,9 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 min_len)
 	u64 scratch_gpa_beg, scratch_gpa_end;
 	void *scratch_va;
 
+	if (WARN_ON_ONCE(!min_len))
+		goto e_scratch;
+
 	scratch_gpa_beg = svm->sev_es.sw_scratch;
 	if (!scratch_gpa_beg) {
 		pr_err("vmgexit: scratch gpa not provided\n");
-- 
2.54.0