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=1793972398; b=OzOSMoQ+CVO3bBpaAsAQv3BLUrF+KKwkKr6pBkzBV7b9TbIh99mune+n0KLXZJQItdTX AeKS4XJnBfH6se58u+rKD+xVsjx1HnJSRjV61b//b7HllislzjKIKjkURhEkEKceguMrG e75r8TC3RrHzBuVZGeLZmOl7DUgsNMEhp28xg5V02vK8ANeRY794IGZzATknOyHeSEvxm iLSrztaBnivre4Gb5/Cn2yuDKW4eGkYF/ljXoL0TEujWcwftbCheWEz7Duq8PxZHj5DTZ zUszc/nbWYD2xTgI/ra4CE/uqG4kbdu/xqvze4iELOBBhw/sBhKQQWVQgKi0sl0YBTQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793972398; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=tM69lu+QIRcJZ/PVIokUvzzLkJJVQ9q3o5Fv8bgq5Mk=; b=06KEJNKZNUDexJKK7HLpDhk1Q9801erqnBWCzk0ucPJwX1Gpx5KzK51SApzizDdVdhsf rAfQxZD2dLDN0Zs8nbMLayHY8y4pKlcWzlszHT39bHMN+xUle4w5yr1PDMwre8AxuI01I clz/dA/clLnvSnfb6VjCKlI9CqcyysnTHLK9u4G4KjiKWcHiQmXWCFm9ioy+iGKa8WeJP x6Yu32SKeilBB59NZ3+1Qh/rBVF5koqJyJReRurHJzCWCVW8ORSBwmujimXB8q0qrOyBe QMP2ZROpqcRFnvlLj9ffQBxWisYfStzxKR/6DQeHEJtk0tA+MD701dq3PeVx6YZVEBw== 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=Eae2fZi1; 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 D6CD2606A333 for ; Fri, 6 Nov 2026 13:39:57 +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=Eae2fZi1 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 289AD1F008A2; Fri, 6 Nov 2026 13:39:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793972397; bh=tM69lu+QIRcJZ/PVIokUvzzLkJJVQ9q3o5Fv8bgq5Mk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Eae2fZi16aO5/MqMfU8O3EBpv5BaYwddU9s8eds6ZShuQsmU8IZqoUubXOHyKdbHO bJZXVhSyZpSPcuRgmdLDmXmaePwbxxsJ9h29vsQKkuY4ukTUVP+KkxOCN6A4k9fWto 7iqZ12a3TuKjSkstPJhunhOEHHaqg22OWn9iYfPH8uJBmJui1grRtMpbLMiqThBmha tZERCBRH3kro/Ln+O85havri20xzzpB9/9K1v5x4cCy5TcVxo6nMVzsE22k1+1okgJ s2uXRKyGIz/YPK0p5P/RtHRwheJWttahfsBM26zJiP9m102srDmK71/LGHqXzeyN81 rQ6OzKjKqb92A== From: Sasha Levin To: stable@vger.kernel.org Cc: Sean Christopherson , Yosry Ahmed , Stefan Teodorescu , Sasha Levin Subject: [PATCH 6.12.y] KVM: nSVM: Reject KVM_SET_NESTED_STATE if L1 has EFER.LMA=1 && EFER.LME=0 Date: Fri, 6 Nov 2026 08:39:55 -0500 Message-ID: <20261106133924.248699-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110437-payer-attire-6993@gregkh> References: <2026110437-payer-attire-6993@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 for __nested_vmcb_check_save() without the third argument ] 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 e2e9ab0858858..3c9c20d7855fe 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -1763,6 +1763,7 @@ 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