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 7C7E9C433EF for ; Mon, 7 Mar 2022 16:45:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237612AbiCGQpy (ORCPT ); Mon, 7 Mar 2022 11:45:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237287AbiCGQpx (ORCPT ); Mon, 7 Mar 2022 11:45:53 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C3B68E1AA; Mon, 7 Mar 2022 08:44:58 -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 1FF29B8162B; Mon, 7 Mar 2022 16:44:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70865C340F6; Mon, 7 Mar 2022 16:44:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646671495; bh=+lMbhkKgsCWNtZnEkoIXQadhDs5xopjEiqcvXcXUsrI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b5CrvhCv9OZOlezkIrShag5TNQObmfRqwGexTpcHcGYSJMp1OFQJREjB45z/GSsAT 34fOuRUy+pSTc9q2/jAfvGWsMCgtfmATdlCdotlxq/SywLrfFClyAGw94j8Wh7+PFB 7pdCElnKDWcqkZwSju/1ewAT5U4DHgpKBFjTw8aOIRIB4mkOfP8qV/PBIBN/vnbUrQ UWg3qmOnkefIF/SlKPfca71BCp5jI1SsUSlnnuBuwOisDWDBj8ODJZo1bCCydDB8w0 DnqgINrvevtzppau6uDs/LXM8uiRevOTjz43BTzJfL5eE+ksYCfpdw9z7thRFWPw/T 8UbqOt6/0pQPw== Date: Mon, 7 Mar 2022 18:44:15 +0200 From: Jarkko Sakkinen To: James Bottomley Cc: Sergey Temerkhanov , Peter Huewe , Jason Gunthorpe , Jerry Snitselaar , linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] tpm: Rework open/close/shutdown to avoid races Message-ID: References: <20201215133801.546207-1-s.temerkhanov@gmail.com> <120839d2925750e278810b2ad211f5465638f7b0.camel@HansenPartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <120839d2925750e278810b2ad211f5465638f7b0.camel@HansenPartnership.com> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Mon, Mar 07, 2022 at 11:22:27AM -0500, James Bottomley wrote: > On Mon, 2022-03-07 at 17:41 +0200, Jarkko Sakkinen wrote: > [...] > > James, would it possible for you to construct a proper patch from > > this and send it so we could include it to the next PR (use my tree > > as baseline)? > > Sure, There's not really any identifiable patch for a fixes tag, since > the race really always existed. > > How about the below. > > James > > -------------------8>8>8><8<8<8------------------ > > From 3e0e640e47e5728b68693c5d45bf3cdd0bff48ca Mon Sep 17 00:00:00 2001 > From: James Bottomley > Date: Mon, 7 Mar 2022 11:16:55 -0500 > Subject: [PATCH] tpm: use try_get_ops() in tpm-space.c > > 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 > --- > 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! LGTM. Reviewed-by: Jarkko Sakkinen BR, Jarkko