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=-8.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 EA6F0C433EB for ; Tue, 14 Jul 2020 09:33:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CAC4C208C3 for ; Tue, 14 Jul 2020 09:33:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PUZRD7Zo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726845AbgGNJdC (ORCPT ); Tue, 14 Jul 2020 05:33:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725952AbgGNJdB (ORCPT ); Tue, 14 Jul 2020 05:33:01 -0400 Received: from mail-ed1-x543.google.com (mail-ed1-x543.google.com [IPv6:2a00:1450:4864:20::543]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5681C061755; Tue, 14 Jul 2020 02:33:00 -0700 (PDT) Received: by mail-ed1-x543.google.com with SMTP id dm19so16325682edb.13; Tue, 14 Jul 2020 02:33:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=4hx30PqqoaKCTO0tMV5MXPy9WV4JOGXHT29cx4BAmGo=; b=PUZRD7ZoJoGcBKUQ//Po15bwuf7dQgrMkN+LsH1vGn+Wu+CPT+g+1ecewCvcnztIQ2 Zr4cI4eZ1MrETF11GT/frURS9Hw9hMFiEj2RVZWvs6sjop4lrpEk2ap67NUS7n4q4MpM h7PLhp82Z1DnvX9DQTD3RXo88dBx8f2W4Kjtsawk/okiXD48p9YZzZh4vRdRY7aZUE+t o+oc98a4PzwjA3FoDxNMWnWOrcgD9r1tvaUb2zAGaNFrfsZ4sISFsSkh6zgDFEDdY7UH dIafe65vWNWVDgvxDX5icgA06I7IMkr7Ob2/N82waLw2dR23WPdSpOMrvbWH8pwKsQGr 5uwg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=4hx30PqqoaKCTO0tMV5MXPy9WV4JOGXHT29cx4BAmGo=; b=iH9KBas7rVwtE5c2ouz1GWQ9+jV8L+q7S89moTnS5nN5a+kAJXDC4N6N8D4qkjxzJe PhQmvdJ6RSBnjUtkVGpJHMKTyJNhsonkmz/iv+IiyJTq/giPpiiSEey5iS3pNFFI/DJg 87zuZSY+8LoA/PpDIJWZ+TJG1QQLhq5VB4cb/njCcyH6hdR1Ffo2lcFzMPQXertlH1fD xXc61XWbcdSuDqa3j1k9EAJ9wyU8pH07hW201nY62CigwsiFzl0vlNmDQ7N4ZI5JASz6 wJ6dSKmz4fF/qvzFgPNkpw40HafOEfwyXzjDwFLjfr8VveNu1dPtD5VcD+xXf10Auyz4 dmeQ== X-Gm-Message-State: AOAM5326K1wRGXarjQDrb8+RHiQJYzrz8Il8FEtV837Tm5DHIVtTs5dz uWgNJIQV8OBEx1qcZxOKw7E= X-Google-Smtp-Source: ABdhPJxQMpKEO/TmGr4t3/ZxNmff8nGv0ouAGV0vHWdU8pzoRUZBJ8ps7/OmisdmObnGZ/BxXqvGAw== X-Received: by 2002:a05:6402:1592:: with SMTP id c18mr3741523edv.258.1594719179492; Tue, 14 Jul 2020 02:32:59 -0700 (PDT) Received: from localhost ([62.96.65.119]) by smtp.gmail.com with ESMTPSA id t6sm12170365ejc.40.2020.07.14.02.32.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jul 2020 02:32:57 -0700 (PDT) Date: Tue, 14 Jul 2020 11:32:56 +0200 From: Thierry Reding To: Jon Hunter Cc: Mathias Nyman , Greg Kroah-Hartman , linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 2/2] usb: tegra: Fix zero length memory allocation Message-ID: <20200714093256.GG141356@ulmo> References: <20200712102837.24340-1-jonathanh@nvidia.com> <20200712102837.24340-2-jonathanh@nvidia.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="DNUSDXU7R7AVVM8C" Content-Disposition: inline In-Reply-To: <20200712102837.24340-2-jonathanh@nvidia.com> User-Agent: Mutt/1.14.4 (2020-06-18) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --DNUSDXU7R7AVVM8C Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Jul 12, 2020 at 11:28:37AM +0100, Jon Hunter wrote: > After commit cad064f1bd52 ("devres: handle zero size in devm_kmalloc()") > was added system suspend started failing on Tegra186. The kernel log > showed that the Tegra XHCI driver was crashing on entry to suspend when > attemptin the save the USB context. The problem is caused because we > are trying to allocate a zero length array for the IPFS context on > Tegra186 and following commit cad064f1bd52 ("devres: handle zero size > in devm_kmalloc()") this now causes a NULL pointer deference crash > when we try to access the memory. Fix this by only allocating memory > for both the IPFS and FPCI contexts when required. >=20 > Cc: stable@vger.kernel.org >=20 > Fixes: 5c4e8d3781bc ("usb: host: xhci-tegra: Add support for XUSB context= save/restore") >=20 > Signed-off-by: Jon Hunter > --- > drivers/usb/host/xhci-tegra.c | 22 ++++++++++++++-------- > 1 file changed, 14 insertions(+), 8 deletions(-) Actually it would seem to me that this is no longer a bug after your fix in patch 1. We only ever access tegra->context.ipfs if tegra->soc->ipfs.num_offsets > 0, so the special ZERO_SIZE_PTR case will not actually cause an issue anymore. The reason why this was crashing was because tegra->context.fpci was allocated with a zero size (because of the bug that you fixed in patch 1) and then that zero-size pointer was dereferenced because the code was correctly checking for tegra->soc->fpci.num_offsets > 0 in the context save and restore. So I don't think there's a bug here. It's not wrong to allocate a zero- size buffer. It's only a bug to then go and dereference it. Are you still seeing the issue if you leave out this patch and only apply patch 1? 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