From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D47D415E83 for ; Mon, 23 Oct 2023 11:37:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="t+zRSMgK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02C00C433C9; Mon, 23 Oct 2023 11:37:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698061040; bh=dbNxpTiaycmt+9SX9nAsTYyKInsEnDsi2fnM8IUVoms=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=t+zRSMgKPDskRTdsmxGRfkHBWEy5+3FaEa/E4+JhC3sKTpgYFsiCNNf3Rb8lOx693 rtz4p6mof/kEl+a5Ob4j7XO9yAJoVAxoZW7ZmFSOwbqmxkwzo5A2exZyyGdhUMzMty l04Ck/BhyHyjSFz8CHr5aj7lryGZBhVbCNbq77FE= 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 5.15 015/137] x86/sev: Disable MMIO emulation from user mode Date: Mon, 23 Oct 2023 12:56:12 +0200 Message-ID: <20231023104821.451137647@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231023104820.849461819@linuxfoundation.org> References: <20231023104820.849461819@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-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 @@ -1004,6 +1004,9 @@ static enum es_result vc_handle_mmio(str enum es_result ret; long *reg_data; + if (user_mode(ctxt->regs)) + return ES_UNSUPPORTED; + switch (insn->opcode.bytes[0]) { /* MMIO Write */ case 0x88: