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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 65876C2BA19 for ; Wed, 15 Apr 2020 22:45:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3BACC20784 for ; Wed, 15 Apr 2020 22:45:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="iJU1m8SK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387511AbgDOWpq (ORCPT ); Wed, 15 Apr 2020 18:45:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1732976AbgDOWpd (ORCPT ); Wed, 15 Apr 2020 18:45:33 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A90A4C061A0C for ; Wed, 15 Apr 2020 15:45:33 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id g6so648273pgs.9 for ; Wed, 15 Apr 2020 15:45:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:mime-version :content-transfer-encoding; bh=hk3FQvRPPps1Uxi4cD6hTJblVzZpBfLo8gEJSgewU+k=; b=iJU1m8SKgYHTmnv3/nRUH7LiYPN1jT883fXNggZGozl+mR/plO1qAh72026IYeUnQe WEiouZLk37XHIff87PbPArkP5mnuLNhtMyeyk9oKvkz9gcJYq/XaQz8RnDp80HZ6/F/u EnaLMbh1EBlTCgymu60TB67+4mmk53SV5fbjO4V8bHUmkgUfYI5Mh9jCUpO0GVvj9Obn MBh4+NA6uUg7Wrg2jLVHXf4jsGJWYktrOQgyhzq2Fc4h6cbn5jMh1/mZl5qRaCm3fHad WuOS2g2Lm8Iimocfoh/W4cgX+z+OqEIIGy3YNUu0J1zMSYilcwppwrcxLcKg6pmYVqEk cVZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:mime-version :content-transfer-encoding; bh=hk3FQvRPPps1Uxi4cD6hTJblVzZpBfLo8gEJSgewU+k=; b=jjjsWi8ftviegW+Z5T4c3eqnIjYUoaPbKBS361jr/ay71kSGF/C+P6t03Z3giOL9Ga gAMi33dZVDfMJdpAnVHWOGqlt28bBPUu/WCcGopS50NUWvGgHAc3cVJjI3fr8KIxMBb6 1MbDt+kXVSxig28qGPbBF376xyZMrqJpj8hfzSBedM+qVnAR2TY7jMq4xCIZUiefH5jx c1RaoqZ03TgPBludI4cI0wzYUwO/rfMN68+LjtBt1lhmtw0uRy6d84PaCz0riNbZMBx2 32oIu+KdGc03PIOgKHzNMOf/1+uEAbHenbxUKtWzWCFYGQ8eAzKZLUcE5keAnCOUw1Bg MsfA== X-Gm-Message-State: AGi0PuYDaXbtfwZg6cW7c0NlUG4tjxqwAGRsZyqYKSMdlYjyY9uG+fp0 9ro/8Zq/2EIdEsbvTrcrWiW5M4yczKE= X-Google-Smtp-Source: APiQypL0zoz0gXpIT2NtDNWV6U82yFfa3jetowhmtl+UG/LSPnz1jR69RrDC86Rv0uLPRFQEKm1s6A== X-Received: by 2002:aa7:8a9a:: with SMTP id a26mr17134973pfc.77.1586990732972; Wed, 15 Apr 2020 15:45:32 -0700 (PDT) Received: from vader.tfbnw.net ([2620:10d:c090:400::5:b0c6]) by smtp.gmail.com with ESMTPSA id j16sm12593323pgi.40.2020.04.15.15.45.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2020 15:45:32 -0700 (PDT) From: Omar Sandoval To: Peter Huewe , Jarkko Sakkinen , Jason Gunthorpe , linux-integrity@vger.kernel.org Subject: [PATCH] tpm_tis: work around status register bug in STMicroelectronics TPM Date: Wed, 15 Apr 2020 15:45:22 -0700 Message-Id: <6c55d7c1fb84e5bf2ace9f05ec816ef67bd873e1.1586990595.git.osandov@fb.com> X-Mailer: git-send-email 2.26.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Omar Sandoval We've encountered a particular model of STMicroelectronics TPM that transiently returns a bad value in the status register. This causes the kernel to believe that the TPM is ready to receive a command when it actually isn't, which in turn causes the send to time out in get_burstcount(). In testing, reading the status register one extra time convinces the TPM to return a valid value. Signed-off-by: Omar Sandoval --- drivers/char/tpm/tpm_tis_core.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c index 27c6ca031e23..277a21027fc7 100644 --- a/drivers/char/tpm/tpm_tis_core.c +++ b/drivers/char/tpm/tpm_tis_core.c @@ -238,6 +238,18 @@ static u8 tpm_tis_status(struct tpm_chip *chip) rc = tpm_tis_read8(priv, TPM_STS(priv->locality), &status); if (rc < 0) return 0; + /* + * Some STMicroelectronics TPMs have a bug where the status register is + * sometimes bogus (all 1s) if read immediately after the access + * register is written to. Bits 0, 1, and 5 are always supposed to read + * as 0, so this is clearly invalid. Reading the register a second time + * returns a valid value. + */ + if (unlikely(status == 0xff)) { + rc = tpm_tis_read8(priv, TPM_STS(priv->locality), &status); + if (rc < 0) + return 0; + } return status; } -- 2.26.1