From patchwork Wed Mar 27 18:32:38 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tadeusz Struk X-Patchwork-Id: 10873847 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 51D64139A for ; Wed, 27 Mar 2019 18:32:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3B98E28A00 for ; Wed, 27 Mar 2019 18:32:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2F75328B6D; Wed, 27 Mar 2019 18:32:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A149428A00 for ; Wed, 27 Mar 2019 18:32:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391651AbfC0Scj (ORCPT ); Wed, 27 Mar 2019 14:32:39 -0400 Received: from mga17.intel.com ([192.55.52.151]:46956 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390457AbfC0Scj (ORCPT ); Wed, 27 Mar 2019 14:32:39 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Mar 2019 11:32:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,277,1549958400"; d="scan'208";a="218112858" Received: from tstruk-mobl1.jf.intel.com ([10.7.196.61]) by orsmga001.jf.intel.com with ESMTP; 27 Mar 2019 11:32:38 -0700 Subject: [PATCH v4] tpm: fix an invalid condition in tpm_common_poll From: Tadeusz Struk To: jarkko.sakkinen@linux.intel.com Cc: grawity@gmail.com, James.Bottomley@HansenPartnership.com, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, tadeusz.struk@intel.com Date: Wed, 27 Mar 2019 11:32:38 -0700 Message-ID: <155371155820.17863.10580533125620125669.stgit@tstruk-mobl1.jf.intel.com> User-Agent: StGit/unknown-version MIME-Version: 1.0 Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The poll condition should only check response_length, because reads should only be issued if there is data to read. The response_read flag only prevents double writes. The problem was that the write set the response_read to false, enqued a tpm job, and returned. Then application called poll which checked the response_read flag and returned EPOLLIN. Then the application called read, but got nothing. After all that the async_work kicked in. Added also mutex_lock around the poll check to prevent other possible race conditions. Cc: stable@vger.kernel.org Fixes: 9488585b21bef0df12 ("tpm: add support for partial reads") Reported-by: Mantas Mikulėnas Tested-by: Mantas Mikulėnas Signed-off-by: Tadeusz Struk Reviewed-by: Jarkko Sakkinen --- drivers/char/tpm/tpm-dev-common.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c index 5eecad233ea1..744b0237300a 100644 --- a/drivers/char/tpm/tpm-dev-common.c +++ b/drivers/char/tpm/tpm-dev-common.c @@ -203,12 +203,19 @@ __poll_t tpm_common_poll(struct file *file, poll_table *wait) __poll_t mask = 0; poll_wait(file, &priv->async_wait, wait); + mutex_lock(&priv->buffer_mutex); - if (!priv->response_read || priv->response_length) + /* + * The response_length indicates if there is still response + * (or part of it) to be consumed. Partial reads decrease it + * by the number of bytes read, and write resets it the zero. + */ + if (priv->response_length) mask = EPOLLIN | EPOLLRDNORM; else mask = EPOLLOUT | EPOLLWRNORM; + mutex_unlock(&priv->buffer_mutex); return mask; }