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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E247AC433DF for ; Mon, 29 Jun 2020 21:46:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C445620780 for ; Mon, 29 Jun 2020 21:46:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593467206; bh=Uf1bd+6LsOrQ0zPDM+2/FRJU4EgTQQASMeTpIMW2X7U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Oay/0rUEYvmYeJIPaiZjyO4AKJTd8t3xVKAAk2XY0Z/Duq72G6hDqBBZD65RvuRc9 TAlG/YZQyZxoqZRf106xp8EQfoeizFcFpRSdJVd9gmp0x0gnbzwIvULf9ovt80qrrW vu2cS7wvFVqOKsMwqQP8Ic+6r+xMv0mJmbmexsac= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404153AbgF2Vqc (ORCPT ); Mon, 29 Jun 2020 17:46:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:56786 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726767AbgF2Sft (ORCPT ); Mon, 29 Jun 2020 14:35:49 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 44588246AD; Mon, 29 Jun 2020 15:20:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593444002; bh=Uf1bd+6LsOrQ0zPDM+2/FRJU4EgTQQASMeTpIMW2X7U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L/Fe4r+oKb+qdG6RWJf/yWYgFA0Q0+iZGRIqD7vEnOGvgvR6pVvJEN2yCS4Eh6M0p wQlU5WxpGbEA4kxkEmhEaXYvZ0ID3kuqKbz8XRfSF78XRgLoYgLlcGucm668LLmGiW MXToBlJ69fVQ7uZ62rGi2BUjwqIN7ESmpNAfFPyU= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Fabian Vogt , Ard Biesheuvel , Sasha Levin Subject: [PATCH 5.7 108/265] efi/tpm: Verify event log header before parsing Date: Mon, 29 Jun 2020 11:15:41 -0400 Message-Id: <20200629151818.2493727-109-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200629151818.2493727-1-sashal@kernel.org> References: <20200629151818.2493727-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.7.7-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-5.7.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 5.7.7-rc1 X-KernelTest-Deadline: 2020-07-01T15:14+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Fabian Vogt [ Upstream commit 7dfc06a0f25b593a9f51992f540c0f80a57f3629 ] It is possible that the first event in the event log is not actually a log header at all, but rather a normal event. This leads to the cast in __calc_tpm2_event_size being an invalid conversion, which means that the values read are effectively garbage. Depending on the first event's contents, this leads either to apparently normal behaviour, a crash or a freeze. While this behaviour of the firmware is not in accordance with the TCG Client EFI Specification, this happens on a Dell Precision 5510 with the TPM enabled but hidden from the OS ("TPM On" disabled, state otherwise untouched). The EFI firmware claims that the TPM is present and active and that it supports the TCG 2.0 event log format. Fortunately, this can be worked around by simply checking the header of the first event and the event log header signature itself. Commit b4f1874c6216 ("tpm: check event log version before reading final events") addressed a similar issue also found on Dell models. Fixes: 6b0326190205 ("efi: Attempt to get the TCG2 event log in the boot stub") Signed-off-by: Fabian Vogt Link: https://lore.kernel.org/r/1927248.evlx2EsYKh@linux-e202.suse.de Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1165773 Signed-off-by: Ard Biesheuvel Signed-off-by: Sasha Levin --- include/linux/tpm_eventlog.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h index c253461b1c4e6..96d36b7a13440 100644 --- a/include/linux/tpm_eventlog.h +++ b/include/linux/tpm_eventlog.h @@ -81,6 +81,8 @@ struct tcg_efi_specid_event_algs { u16 digest_size; } __packed; +#define TCG_SPECID_SIG "Spec ID Event03" + struct tcg_efi_specid_event_head { u8 signature[16]; u32 platform_class; @@ -171,6 +173,7 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event, int i; int j; u32 count, event_type; + const u8 zero_digest[sizeof(event_header->digest)] = {0}; marker = event; marker_start = marker; @@ -198,10 +201,19 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event, count = READ_ONCE(event->count); event_type = READ_ONCE(event->event_type); + /* Verify that it's the log header */ + if (event_header->pcr_idx != 0 || + event_header->event_type != NO_ACTION || + memcmp(event_header->digest, zero_digest, sizeof(zero_digest))) { + size = 0; + goto out; + } + efispecid = (struct tcg_efi_specid_event_head *)event_header->event; /* Check if event is malformed. */ - if (count > efispecid->num_algs) { + if (memcmp(efispecid->signature, TCG_SPECID_SIG, + sizeof(TCG_SPECID_SIG)) || count > efispecid->num_algs) { size = 0; goto out; } -- 2.25.1