From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B3B1C433F5 for ; Wed, 27 Apr 2022 15:56:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240999AbiD0P7l (ORCPT ); Wed, 27 Apr 2022 11:59:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56838 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240605AbiD0P6P (ORCPT ); Wed, 27 Apr 2022 11:58:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0283D78385; Wed, 27 Apr 2022 08:54:38 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E5F4361B49; Wed, 27 Apr 2022 15:54:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 91FD7C385AC; Wed, 27 Apr 2022 15:54:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1651074874; bh=sl9Pb4DXc7gRUL5a3faT/UaiHOw0prFpxyvgZ2bEQhI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H8yrB8l76l6jqX8Q2FBLgokqrXF26yrz3ERh5gkmRxdGypegGx1CfaLo1ud471PiB wynu17fheQ6JsYU9SfwojBquMC67PmckhMi5ILjixZGNR66VvjDQ+dDi1A4aRn+f7c l0ycK9n2FsA/dQa1vGm5zQAy68Srt8wUel3KrTuG64lT2LnK+iHiBvUNXdediLwhKO NnvZ8OYJpnWZYRnbu0f82yxK+hBUSy0ZGiZdxMimhpLGUr2H5uugT41hkaQeBzDPAq pQ2GNQDFz3pZyDGk+OPnbaHIvPTUTg1tWKnG8jiovWi7/3FjRl3j4owitpMgPJWEel 30ogcDuF1zmcg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Sasha Levin , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org Subject: [PATCH MANUALSEL 5.15 6/7] KVM: x86/mmu: avoid NULL-pointer dereference on page freeing bugs Date: Wed, 27 Apr 2022 11:54:26 -0400 Message-Id: <20220427155431.19458-6-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220427155431.19458-1-sashal@kernel.org> References: <20220427155431.19458-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Paolo Bonzini [ Upstream commit 9191b8f0745e63edf519e4a54a4aaae1d3d46fbd ] WARN and bail if KVM attempts to free a root that isn't backed by a shadow page. KVM allocates a bare page for "special" roots, e.g. when using PAE paging or shadowing 2/3/4-level page tables with 4/5-level, and so root_hpa will be valid but won't be backed by a shadow page. It's all too easy to blindly call mmu_free_root_page() on root_hpa, be nice and WARN instead of crashing KVM and possibly the kernel. Reviewed-by: Sean Christopherson Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/mmu/mmu.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 34e828badc51..806f9d42bcce 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3314,6 +3314,8 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa, return; sp = to_shadow_page(*root_hpa & PT64_BASE_ADDR_MASK); + if (WARN_ON(!sp)) + return; if (is_tdp_mmu_page(sp)) kvm_tdp_mmu_put_root(kvm, sp, false); -- 2.35.1