From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793971472; b=PqMPaLBxZ78dBcsyH5H7JquREDDyBVf00dqV/YdPIpfq5LF6T/vog+FUVai0lRuylksx vAJlbDfoXtR0BfQjn+aLl3De+MLDbx3gy2uS3c8Pi6kHtfQiUc4busOMbsR4w5k3kIkh+ 4WYE1E7Lp4cPnlG5ZXAq1BttCCUyt8kQc+LSny2NvmsOWMju3m7K2ir+8nzxFLnYCpQHF xuX9sEGqEByI5D60UP89jlGzosi918xe9zphsAxhZbnpbB1yF33uQMCDZcQeYJNhwlXLi qCWRzmQb7yaKqmftVr8OhK7w4F1er5IlSgQmHn6fm3hFwTojPaSen6g2MEFEFzfMBSg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793971472; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=rhkpp6PE4FDH+icC0oc4FBw/hVaWjE/hr09qmQ6ff2M=; b=u7jejluYcTUNRz60bYN2qt1DocM6fl+56i95teUvt3h9kUutPZjlARJh3h6MtB+e7EAw VZSbNZDZUga+vGcMy4RepGejdLP9L9IhfMDtPHobKmTyJdSB8EY8J3zJBN0tnsFpsd0nT 6NLOPSU1Prgso85HltfU0ltIEe71J2cYT3Do1oKnpWrGjnGn1ESfHC3wAq7Lr2CXh5V6n Ejp12zhhNhazQAy+fDJKrehZjUlTii5RjhV5bbwQep7gjg1Wyds3hFJmXLdHBaJ9m41h0 JXceY4Ce7LOMNFj0IXK16L3Qwc9Knwyz+tf9ZTwr9L4rTxCruqyInR7v/ePbHHJYV0w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VMh7dEIA; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C6271606A326 for ; Fri, 6 Nov 2026 13:24:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VMh7dEIA Received: by smtp.kernel.org (Postfix) with ESMTPSA id C82FD1F0089F; Fri, 6 Nov 2026 13:24:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793971471; bh=rhkpp6PE4FDH+icC0oc4FBw/hVaWjE/hr09qmQ6ff2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VMh7dEIANOzUzlFgpzqf7BrvZ5PpvNY6MZ19gaFh8IJrljpxJUE1wYC4L3T9/if7p qVg1O8lEhIopePE+7d++HBWmvQmUEw4OGWlbwnspODiHr6K/AFIjp/Zrrx2JRZQ59H GKSKqVyOGJuuf+v2CmJHRtSpDvALmc762BH69WrtRNcH/VjUkl1It9T0EFL5TyzbEd yPAg2cnG1QF53X89tPwPe2tu/M/qNAqOd2z/4YPutKLViLIMZo0yR9e30zEhn+7QQ2 0XGCqFVMxvKu/Mv9mBsoy/ipqGFd9l3S9gUs03sCDt+ecvVvdGYiWLtHDfz4IW5PXJ sD0yfO8RR0cNA== From: Sasha Levin To: stable@vger.kernel.org Cc: Sean Christopherson , Yosry Ahmed , Stefan Teodorescu , Sasha Levin Subject: [PATCH 6.18.y] KVM: nSVM: Reject KVM_SET_NESTED_STATE if L1 has EFER.LMA=1 && EFER.LME=0 Date: Fri, 6 Nov 2026 08:24:29 -0500 Message-ID: <20261106132304.65484-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110436-sequel-runner-492c@gregkh> References: <2026110436-sequel-runner-492c@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Sean Christopherson [ Upstream commit 5dc500a354cc8e109df678076ae3488094649468 ] Reject KVM_SET_NESTED_STATE if the incoming L1 host state has what is effectively an impossible EFER combination of LMA=1 but LME=0, i.e. if the state says long mode is active but not enabled. Unlike VMX, SVM doesn't have an explicit consistent check for the illegal combination; presumably hardware simply ignores EFER.LMA if EFER.LME=0. Unfortunately, KVM doesn't ignore EFER.LMA in this case and consumes the illegal state when constructing the shadow MMU for L2. E.g. if userspace also clears CR4.PAE, then kvm_calc_cpu_role() will compute a role with 4 or 5 levels of paging, but shadow_mmu_init_context() will wire up the MMU to use the paging32 template, which maxes out its levels at 2. Note, the "real badness" is effectively the same as what happened with the nVMX bug fixed by commit 112e66017bff ("KVM: nVMX: add missing consistency checks for CR0 and CR4"). Unfortunately, the sanity check added by commit 72e2fb24a0b0 ("KVM: x86/mmu: Bug the VM if a vCPU ends up in long mode without PAE enabled") doesn't work for this case, since L2 state is active at the time of the page fault, but it's L1 that has the bad state. Fixes: cc440cdad5b7 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE") Cc: stable@vger.kernel.org Cc: Yosry Ahmed Reported-by: Stefan Teodorescu Link: https://patch.msgid.link/20260902232028.2767071-2-seanjc@google.com Signed-off-by: Sean Christopherson [ sashal: adjusted context to retain the two-argument __nested_vmcb_check_save() helper instead of nested_vmcb_check_save() ] Signed-off-by: Sasha Levin --- arch/x86/kvm/svm/nested.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 064a2bb9cf8ed..49cc457a4c370 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1880,6 +1880,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, if (!(save->cr0 & X86_CR0_PG) || !(save->cr0 & X86_CR0_PE) || (save->rflags & X86_EFLAGS_VM) || + ((save->efer & EFER_LMA) && !(save->efer & EFER_LME)) || !__nested_vmcb_check_save(vcpu, &save_cached)) goto out_free; -- 2.53.0