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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 38860C433E1 for ; Thu, 18 Jun 2020 14:38:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1B15720773 for ; Thu, 18 Jun 2020 14:38:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730872AbgFROiy (ORCPT ); Thu, 18 Jun 2020 10:38:54 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55549 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726981AbgFROiy (ORCPT ); Thu, 18 Jun 2020 10:38:54 -0400 Received: from 1.general.cking.uk.vpn ([10.172.193.212]) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jlvgo-0002Gk-Uo; Thu, 18 Jun 2020 14:38:51 +0000 Subject: Re: [PATCH] drm/arm: fix unintentional integer overflow on left shift To: Garrit Franke , Liviu Dudau Cc: David Airlie , kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20200618100400.11464-1-colin.king@canonical.com> <20200618121405.GJ159988@e110455-lin.cambridge.arm.com> <5d08fbec-75d8-d9a9-af61-e6ab98e77c80@canonical.com> <20200618142106.GK159988@e110455-lin.cambridge.arm.com> From: Colin Ian King Autocrypt: addr=colin.king@canonical.com; prefer-encrypt=mutual; keydata= mQINBE6TJCgBEACo6nMNvy06zNKj5tiwDsXXS+LhT+LwtEsy9EnraKYXAf2xwazcICSjX06e fanlyhB0figzQO0n/tP7BcfMVNG7n1+DC71mSyRK1ZERcG1523ajvdZOxbBCTvTitYOy3bjs +LXKqeVMhK3mRvdTjjmVpWnWqJ1LL+Hn12ysDVVfkbtuIm2NoaSEC8Ae8LSSyCMecd22d9Pn LR4UeFgrWEkQsqROq6ZDJT9pBLGe1ZS0pVGhkRyBP9GP65oPev39SmfAx9R92SYJygCy0pPv BMWKvEZS/7bpetPNx6l2xu9UvwoeEbpzUvH26PHO3DDAv0ynJugPCoxlGPVf3zcfGQxy3oty dNTWkP6Wh3Q85m+AlifgKZudjZLrO6c+fAw/jFu1UMjNuyhgShtFU7NvEzL3RqzFf9O1qM2m uj83IeFQ1FZ65QAiCdTa3npz1vHc7N4uEQBUxyXgXfCI+A5yDnjHwzU0Y3RYS52TA3nfa08y LGPLTf5wyAREkFYou20vh5vRvPASoXx6auVf1MuxokDShVhxLpryBnlKCobs4voxN54BUO7m zuERXN8kadsxGFzItAyfKYzEiJrpUB1yhm78AecDyiPlMjl99xXk0zs9lcKriaByVUv/NsyJ FQj/kmdxox3XHi9K29kopFszm1tFiDwCFr/xumbZcMY17Yi2bQARAQABtCVDb2xpbiBLaW5n IDxjb2xpbi5raW5nQGNhbm9uaWNhbC5jb20+iQI2BBMBCAAhBQJOkyQoAhsDBQsJCAcDBRUK CQgLBRYCAwEAAh4BAheAAAoJEGjCh9/GqAImsBcP9i6C/qLewfi7iVcOwqF9avfGzOPf7CVr n8CayQnlWQPchmGKk6W2qgnWI2YLIkADh53TS0VeSQ7Tetj8f1gV75eP0Sr/oT/9ovn38QZ2 vN8hpZp0GxOUrzkvvPjpH+zdmKSaUsHGp8idfPpZX7XeBO0yojAs669+3BrnBcU5wW45SjSV nfmVj1ZZj3/yBunb+hgNH1QRcm8ZPICpjvSsGFClTdB4xu2AR28eMiL/TTg9k8Gt72mOvhf0 fS0/BUwcP8qp1TdgOFyiYpI8CGyzbfwwuGANPSupGaqtIRVf+/KaOdYUM3dx/wFozZb93Kws gXR4z6tyvYCkEg3x0Xl9BoUUyn9Jp5e6FOph2t7TgUvv9dgQOsZ+V9jFJplMhN1HPhuSnkvP 5/PrX8hNOIYuT/o1AC7K5KXQmr6hkkxasjx16PnCPLpbCF5pFwcXc907eQ4+b/42k+7E3fDA Erm9blEPINtt2yG2UeqEkL+qoebjFJxY9d4r8PFbEUWMT+t3+dmhr/62NfZxrB0nTHxDVIia u8xM+23iDRsymnI1w0R78yaa0Eea3+f79QsoRW27Kvu191cU7QdW1eZm05wO8QUvdFagVVdW Zg2DE63Fiin1AkGpaeZG9Dw8HL3pJAJiDe0KOpuq9lndHoGHs3MSa3iyQqpQKzxM6sBXWGfk EkK5Ag0ETpMkKAEQAMX6HP5zSoXRHnwPCIzwz8+inMW7mJ60GmXSNTOCVoqExkopbuUCvinN 4Tg+AnhnBB3R1KTHreFGoz3rcV7fmJeut6CWnBnGBtsaW5Emmh6gZbO5SlcTpl7QDacgIUuT v1pgewVHCcrKiX0zQDJkcK8FeLUcB2PXuJd6sJg39kgsPlI7R0OJCXnvT/VGnd3XPSXXoO4K cr5fcjsZPxn0HdYCvooJGI/Qau+imPHCSPhnX3WY/9q5/WqlY9cQA8tUC+7mgzt2VMjFft1h rp/CVybW6htm+a1d4MS4cndORsWBEetnC6HnQYwuC4bVCOEg9eXMTv88FCzOHnMbE+PxxHzW 3Gzor/QYZGcis+EIiU6hNTwv4F6fFkXfW6611JwfDUQCAHoCxF3B13xr0BH5d2EcbNB6XyQb IGngwDvnTyKHQv34wE+4KtKxxyPBX36Z+xOzOttmiwiFWkFp4c2tQymHAV70dsZTBB5Lq06v 6nJs601Qd6InlpTc2mjd5mRZUZ48/Y7i+vyuNVDXFkwhYDXzFRotO9VJqtXv8iqMtvS4xPPo 2DtJx6qOyDE7gnfmk84IbyDLzlOZ3k0p7jorXEaw0bbPN9dDpw2Sh9TJAUZVssK119DJZXv5 2BSc6c+GtMqkV8nmWdakunN7Qt/JbTcKlbH3HjIyXBy8gXDaEto5ABEBAAGJAh8EGAEIAAkF Ak6TJCgCGwwACgkQaMKH38aoAiZ4lg/+N2mkx5vsBmcsZVd3ys3sIsG18w6RcJZo5SGMxEBj t1UgyIXWI9lzpKCKIxKx0bskmEyMy4tPEDSRfZno/T7p1mU7hsM4owi/ic0aGBKP025Iok9G LKJcooP/A2c9dUV0FmygecRcbIAUaeJ27gotQkiJKbi0cl2gyTRlolKbC3R23K24LUhYfx4h pWj8CHoXEJrOdHO8Y0XH7059xzv5oxnXl2SD1dqA66INnX+vpW4TD2i+eQNPgfkECzKzGj+r KRfhdDZFBJj8/e131Y0t5cu+3Vok1FzBwgQqBnkA7dhBsQm3V0R8JTtMAqJGmyOcL+JCJAca 3Yi81yLyhmYzcRASLvJmoPTsDp2kZOdGr05Dt8aGPRJL33Jm+igfd8EgcDYtG6+F8MCBOult TTAu+QAijRPZv1KhEJXwUSke9HZvzo1tNTlY3h6plBsBufELu0mnqQvHZmfa5Ay99dF+dL1H WNp62+mTeHsX6v9EACH4S+Cw9Q1qJElFEu9/1vFNBmGY2vDv14gU2xEiS2eIvKiYl/b5Y85Q QLOHWV8up73KK5Qq/6bm4BqVd1rKGI9un8kezUQNGBKre2KKs6wquH8oynDP/baoYxEGMXBg GF/qjOC6OY+U7kNUW3N/A7J3M2VdOTLu3hVTzJMZdlMmmsg74azvZDV75dUigqXcwjE= Message-ID: <33bcb868-5202-9a59-b4c6-803097cbe620@canonical.com> Date: Thu, 18 Jun 2020 15:38:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/06/2020 15:36, Garrit Franke wrote: > Hi all, newbie here. > Can the BIT macro be safely used on other parts of the kernel as well? > Just using git grep "1 <<" returns a ton of results where bit shifting > is used the old fashioned way. The BIT macro casts the 1 it a UL before shifting so it catches these type of bugs. use BIT_ULL when the result is assigned to a long long. Colin > > Am Do., 18. Juni 2020 um 16:23 Uhr schrieb Liviu Dudau : >> >> On Thu, Jun 18, 2020 at 01:50:34PM +0100, Colin Ian King wrote: >>> On 18/06/2020 13:14, Liviu Dudau wrote: >>>> On Thu, Jun 18, 2020 at 11:04:00AM +0100, Colin King wrote: >>>>> From: Colin Ian King >>>> >>>> Hi Colin, >>>> >>>>> >>>>> Shifting the integer value 1 is evaluated using 32-bit arithmetic >>>>> and then used in an expression that expects a long value leads to >>>>> a potential integer overflow. >>>> >>>> I'm afraid this explanation makes no sense to me. Do you care to explain better what >>>> you think the issue is? If the shift is done as 32-bit arithmetic and then promoted >>>> to long how does the overflow happen? >>> >>> The shift is performed using 32 bit signed math and then assigned to an >>> unsigned 64 bit long. This if the shift is 31 bits then the signed int >>> conversion of 0x80000000 to unsigned long becomes 0xffffffff80000000. >>> If the shift is more than 32 bits then result overflows and becomes 0x0. >> >> You are right, I've missed the fact that it is signed math. Not very likely that >> we are going to ever have 30 or more CRTCs in the driver, but Coverity has no >> way of knowing that. >> >> Acked-by: Liviu Dudau >> >> I will pull this into drm-misc-next today. >> >> Best regards, >> Liviu >> >>> >>> Colin >>> >>>> >>>> Best regards, >>>> Liviu >>>> >>>>> Fix this by using the BIT macro to >>>>> perform the shift to avoid the overflow. >>>>> >>>>> Addresses-Coverity: ("Unintentional integer overflow") >>>>> Fixes: ad49f8602fe8 ("drm/arm: Add support for Mali Display Processors") >>>>> Signed-off-by: Colin Ian King >>>>> --- >>>>> drivers/gpu/drm/arm/malidp_planes.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/arm/malidp_planes.c b/drivers/gpu/drm/arm/malidp_planes.c >>>>> index 37715cc6064e..ab45ac445045 100644 >>>>> --- a/drivers/gpu/drm/arm/malidp_planes.c >>>>> +++ b/drivers/gpu/drm/arm/malidp_planes.c >>>>> @@ -928,7 +928,7 @@ int malidp_de_planes_init(struct drm_device *drm) >>>>> const struct malidp_hw_regmap *map = &malidp->dev->hw->map; >>>>> struct malidp_plane *plane = NULL; >>>>> enum drm_plane_type plane_type; >>>>> - unsigned long crtcs = 1 << drm->mode_config.num_crtc; >>>>> + unsigned long crtcs = BIT(drm->mode_config.num_crtc); >>>>> unsigned long flags = DRM_MODE_ROTATE_0 | DRM_MODE_ROTATE_90 | DRM_MODE_ROTATE_180 | >>>>> DRM_MODE_ROTATE_270 | DRM_MODE_REFLECT_X | DRM_MODE_REFLECT_Y; >>>>> unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) | >>>>> -- >>>>> 2.27.0.rc0 >>>>> >>>> >>> >>> _______________________________________________ >>> dri-devel mailing list >>> dri-devel@lists.freedesktop.org >>> https://lists.freedesktop.org/mailman/listinfo/dri-devel >> >> -- >> ==================== >> | I would like to | >> | fix the world, | >> | but they're not | >> | giving me the | >> \ source code! / >> --------------- >> ¯\_(ツ)_/¯