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 6F3CCC433F5 for ; Tue, 8 Mar 2022 08:30:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344969AbiCHIbc (ORCPT ); Tue, 8 Mar 2022 03:31:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238409AbiCHIbY (ORCPT ); Tue, 8 Mar 2022 03:31:24 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA70A3F8A1; Tue, 8 Mar 2022 00:30:24 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9924FB8179F; Tue, 8 Mar 2022 08:30:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD48FC340EB; Tue, 8 Mar 2022 08:30:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646728222; bh=d4iX8PMKAGFjzqQJsmEWtLrsA3AzOiHHSY+t4oi+qwo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Wyml7Am/nzk+GK45JiukdCoLYjIeuQbDYqgDJxA/Ge5dZXUOoTVH2Kq2PKrmiYcTI mfj0O29ZG+Kgcfel2g5Ymz+Ye7gVpUOrQ2ajEUvtQDt4RitMQINFc/bPSD1qvmq/Xd RyDFqv71c+ndZ6gLyhJYEJRa6mUT7GACA9yJAvFbusIYfiFwpXmVrUo+yH6TBbUxu1 AaHVuYDou1Ld96hJF12vkfaTICg4yL/4zzMJhL7OIe3irpG3NPFTYBDawpnjdbZioh VBvcabxQ2Uad9ERSArFwdCslBGgndE0JcZEwktTeZtSo7MFouUZw2r6Ue30r9Hz6vs wHvETz1aPTaCw== Date: Tue, 8 Mar 2022 10:29:41 +0200 From: Jarkko Sakkinen To: James Bottomley Cc: Sergey Temerkhanov , Peter Huewe , Jason Gunthorpe , Jerry Snitselaar , linux-integrity@vger.kernel.org, linux-kernel Subject: Re: [PATCH] tpm: use try_get_ops() in tpm-space.c Message-ID: References: <3953c743ce7e7fc1db26f5b849b53df671b2f221.camel@HansenPartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3953c743ce7e7fc1db26f5b849b53df671b2f221.camel@HansenPartnership.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 07, 2022 at 03:58:03PM -0500, James Bottomley wrote: > As part of the series conversion to remove nested TPM operations: > > https://lore.kernel.org/all/20190205224723.19671-1-jarkko.sakkinen@linux.intel.com/ > > exposure of the chip->tpm_mutex was removed from much of the upper > level code. In this conversion, tpm2_del_space() was missed. This > didn't matter much because it's usually called closely after a > converted operation, so there's only a very tiny race window where the > chip can be removed before the space flushing is done which causes a > NULL deref on the mutex. However, there are reports of this window > being hit in practice, so fix this by converting tpm2_del_space() to > use tpm_try_get_ops(), which performs all the teardown checks before > acquring the mutex. > > Signed-off-by: James Bottomley > Reviewed-by: Jarkko Sakkinen > --- > drivers/char/tpm/tpm2-space.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c > index 265ec72b1d81..ffb35f0154c1 100644 > --- a/drivers/char/tpm/tpm2-space.c > +++ b/drivers/char/tpm/tpm2-space.c > @@ -58,12 +58,12 @@ int tpm2_init_space(struct tpm_space *space, unsigned int buf_size) > > void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space) > { > - mutex_lock(&chip->tpm_mutex); > - if (!tpm_chip_start(chip)) { > + > + if (tpm_try_get_ops(chip) == 0) { > tpm2_flush_sessions(chip, space); > - tpm_chip_stop(chip); > + tpm_put_ops(chip); > } > - mutex_unlock(&chip->tpm_mutex); > + > kfree(space->context_buf); > kfree(space->session_buf); > } > -- > 2.34.1 > > Thank you! BR, Jarkko