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 A2E5DC001E0 for ; Mon, 23 Oct 2023 11:20:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230433AbjJWLUq (ORCPT ); Mon, 23 Oct 2023 07:20:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233796AbjJWLUn (ORCPT ); Mon, 23 Oct 2023 07:20:43 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60474102 for ; Mon, 23 Oct 2023 04:20:41 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 678FEC433C8; Mon, 23 Oct 2023 11:20:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698060040; bh=H7pA9bR4cQvkhwcWc7mUnvuHitDseZghquK5rc4nMUs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MM+ZO6/NHOWGs4iCEp92WTkC430COq01lgd8HWxMkMUKbY4IqTlZaRjt6ODFa/hi0 TK2ShuCn2lUlJdN2t9G9Nn0gnRHJWA9MMAYT4N4dD2xUoEmS4k+uiLE3a5/BsXsXn5 EAPtREIXwhCeK8dfqviKsixRorpA2WzeDwhZ/QAk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tom Dohrmann , "Borislav Petkov (AMD)" , stable@kernel.org Subject: [PATCH 6.1 021/196] x86/sev: Disable MMIO emulation from user mode Date: Mon, 23 Oct 2023 12:54:46 +0200 Message-ID: <20231023104829.085715836@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231023104828.488041585@linuxfoundation.org> References: <20231023104828.488041585@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Borislav Petkov (AMD)" Upstream commit: a37cd2a59d0cb270b1bba568fd3a3b8668b9d3ba A virt scenario can be constructed where MMIO memory can be user memory. When that happens, a race condition opens between when the hardware raises the #VC and when the #VC handler gets to emulate the instruction. If the MOVS is replaced with a MOVS accessing kernel memory in that small race window, then write to kernel memory happens as the access checks are not done at emulation time. Disable MMIO emulation in user mode temporarily until a sensible use case appears and justifies properly handling the race window. Fixes: 0118b604c2c9 ("x86/sev-es: Handle MMIO String Instructions") Reported-by: Tom Dohrmann Signed-off-by: Borislav Petkov (AMD) Tested-by: Tom Dohrmann Cc: Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/sev.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -1552,6 +1552,9 @@ static enum es_result vc_handle_mmio(str return ES_DECODE_FAILED; } + if (user_mode(ctxt->regs)) + return ES_UNSUPPORTED; + switch (mmio) { case MMIO_WRITE: memcpy(ghcb->shared_buffer, reg_data, bytes);