Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <1c7e171b-e5e8-7197-ddbc-346bac86176d@intel.com>
Date:   Fri, 7 Oct 2022 19:40:36 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.12.0
Subject: Re: [PATCH v13 5/9] drm/i915: Check for integer truncation on
 scatterlist creation
Content-Language: en-US
To:     Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
CC:     <intel-gfx@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        <dri-devel@lists.freedesktop.org>, <mchehab@kernel.org>,
        <chris@chris-wilson.co.uk>, <matthew.auld@intel.com>,
        <thomas.hellstrom@linux.intel.com>, <jani.nikula@intel.com>,
        <nirmoy.das@intel.com>, <airlied@redhat.com>, <daniel@ffwll.ch>,
        <andi.shyti@linux.intel.com>, <andrzej.hajda@intel.com>,
        <mauro.chehab@linux.intel.com>, <linux@rasmusvillemoes.dk>,
        <vitor@massaru.org>, <dlatypov@google.com>,
        <ndesaulniers@google.com>, <trix@redhat.com>,
        <llvm@lists.linux.dev>, <linux-hardening@vger.kernel.org>,
        <linux-sparse@vger.kernel.org>, <nathan@kernel.org>,
        <gustavoars@kernel.org>, <luc.vanoostenryck@gmail.com>
References: <20220928081300.101516-1-gwan-gyeong.mun@intel.com>
 <20220928081300.101516-6-gwan-gyeong.mun@intel.com>
 <CAHk-=wivJwvVbMUKma8600F6qaVLZHT=BY90SEnjiHWw2ZUVEg@mail.gmail.com>
 <202209281102.A86D736@keescook>
From:   Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
In-Reply-To: <202209281102.A86D736@keescook>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bWozTnBaY0E4amE3UG5PZ09ITWd3b0tLcUFrNUhONHBtc0VaOEJSWE9oeVFK?=
 =?utf-8?B?TTdtZFQzaHAyakRqbnBORTFLeUpJaGxKWmdzcXAzbktOU01QZUQxV3dueW1y?=
 =?utf-8?B?TkwzR3QwaWoraXFVZHFIWFlnR3NEdUxoZWtiUnB4c0ZINHRiNW9mTG9xaXMw?=
 =?utf-8?B?cTJ6KzFLdStnbVNvc2dDQkpKM3ZLTXFZc0xSZEdSeURBNmdVKzVEOWpmSmxV?=
 =?utf-8?B?N2NDVFpVWk1pcGF1U0Zyek1KQ2pFeEQxTGZhcHpIMDVnRjMyc0ZhTWROZEJP?=
 =?utf-8?B?RUZlSUVDdDV4cTNTZ1dXeHNUSTNQY3UvT3ZJdXYxb0dYRVRIazdUTi9CY0Js?=
 =?utf-8?B?QkhReEN4M05iSkZ0V04xbkw0cklOU25oWXUwU1RlL1ZCdUU4YmxaRlZlTUx3?=
 =?utf-8?B?TWtTRkFvWWtCeWpzMkdxUHBkTHhVaEdvTjFLeHY2Q2FYNG5TMStNUW90cmtV?=
 =?utf-8?B?NWRyUVp3bDYyeUVlMjRMdVcwLzZOVDN4UC9VMk9panFYcE5iVUtzWlNBY0NQ?=
 =?utf-8?B?My9lRjA5SGhqUnhMK0JlYlY4Nnp2akhIL2pTOXJrTUZXR0ZWdnVlV1pZMFkx?=
 =?utf-8?B?RnJkWDBxZ1dWcWpjR2xWSndhakRmWlZUbWlvZFRwbmpRS2dyWEhVYkM0MHlt?=
 =?utf-8?B?RDJCRmJ5T0RmYmZwTVFPT0c2RTBpOWFIS2pqOXRaOUxuWjlQQTdGOEJwQVN0?=
 =?utf-8?B?alRha01OSGp3c09zck1IQWNQdVJtQktQMEZRZEl0Smh0ZnZJaEs4WlRGMG1I?=
 =?utf-8?B?VjlwemlxZUFvVmNIOGYzSW5sWFAvelNwVHRwNUx3K3MwODJKMlZnS3VxTFJp?=
 =?utf-8?B?RHdyc0oyOHdFRHdiei9MNVdYb0lFeXp4WGVlV1Arb1FFcFh2Nk5STGNzdFN1?=
 =?utf-8?B?alhHQ3Yxams0SmRkWGFlbE8xazlMUGdFV2t2ZkZuOGdYN3JybnJMN3N2eWRE?=
 =?utf-8?B?OFNMbGNJOXlFbHlaSUkrRnV2bThXODlVWjcwbXV6NEJ6d0FDWmhPUUxnK0ZZ?=
 =?utf-8?B?RGtLVVJ1dFJJV2ZxK0g5Nlh3djJBQ0lOSFZUb2xUM2hSZTVKWmZlajR4dzNS?=
 =?utf-8?B?OVNjc3VGZXRXVHpFLzNCVGNlTjJiTjVvL1BLNVNxMXdhZjVPYUtGQU5CbHlF?=
 =?utf-8?B?amhyTncvWXZEU2VNNkxEYmJUTkFaV0lrMmtTWUJWNFZkMlZJYnVtdGY5TG9y?=
 =?utf-8?B?SUFFOVBnUUwvUlgreXNodmxWQmtoZGw3RmluK0VuWXY1bTVoVzNSMm9yTkZz?=
 =?utf-8?B?aWc3bFd2MmxZa2ZacWdUem1lNlVHc1ZiTmw0dVR5U0JTT3g5ZVlzUE9iZ3VM?=
 =?utf-8?B?NHE2REdwdXdEUjBFRUZJeklZUStiVENmaWw2L3krMkFqU2VKTk1vc2h6NkRa?=
 =?utf-8?B?SHZ1MjJCUHhLTnhTaGFMSEcwQmFDcnhuZy9IRDN6ckwybFd2Z005OTJNTmlZ?=
 =?utf-8?B?bVB3TUNwWDQ2amZSUE9SQXFmalB5VTF3SDlBeTkwdkNXd3JxdSsvWFdwV2Jm?=
 =?utf-8?B?S2NLREdmUWpacWNOU0krbVFwTTV5RndVcUlLdlNtQXBRRGFDcHkrRXhxN2FP?=
 =?utf-8?B?b00ySFRIZExrcUY4ckN5RXRaejN0NmxoN0VvVmdyUXJ1NG1LemszeEhpZVZM?=
 =?utf-8?B?UmhRZVpBUmFSeEl3cHhGVGU1S2RBSWVzMlByOCtkWS9ueUVXNUpadUQ0N3c0?=
 =?utf-8?B?T2pHdklhYnVESkU0N25uQmR4TTJQbjJTaTBhVVdGMTFmRlFRYkdxejg4WFJ0?=
 =?utf-8?B?Sm1zb1hhc2FLVXhWVjFZbUkrKytWK3ViSjJzekgyRGdKNVJwb2Z0TWc5WVFQ?=
 =?utf-8?B?ZkJQMXBVZUx0bHF2N0RnQUhSdENheFFjWlZjVG12UEtRa2txWXUrVWZsejBZ?=
 =?utf-8?B?SEtHTHI4ejlxWmlNZjZPSHZiUTdNRUhXMUFDTnJZZk4xQnlmMDZhYVVDQzlD?=
 =?utf-8?B?NTRzVVdFNTJkR21IL1hHTlloR3gyTlg3dUR6NFJtZVRlZjVEblp6QnA4SGJC?=
 =?utf-8?B?VzNMRy81ZmFPVElTU2Y3c0lxam1scDRnNzEyRmR1eENhK2NZY3dVVkhONDA1?=
 =?utf-8?B?UXZEYjd0SGlXeGdyakNQTURSN2VESFNjSlF3MFhQY0tnRkUxclcvTWU0STFk?=
 =?utf-8?B?Tkszc1gxbWpFc1NpN1BaS0p0TXJzbGc5ckVZSldzT1BKTlc5N2p4c1BrajJN?=
 =?utf-8?B?MEE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: b74003b3-885e-4f87-dcc7-08daa882c605
X-MS-Exchange-CrossTenant-AuthSource: CH0PR11MB5409.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Oct 2022 16:41:25.3302
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: OC/tG4ewmci69i4S6Lh5PCqiy8488EkWxbbUetzVfZ8CLxBY7Tw3Tn0kbfTYanNh7LkfTFBrSRDsCwhajGbrvvsXMIkDBTSfduJ/5IMwuko=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR11MB5554
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-9.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,
        RCVD_IN_DNSWL_HI,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,
        SPF_NONE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Linus and Kees, I also understood that I should not make and use the 
macro that performs assignment and checking at the same time, and I will 
drop it and update it.

Kees, the overflows_type() macro had several updates as input from you 
and the community, and there is an advantage when moving to Linux common.
What are your thoughts on continuing to add the overflows_type() macro 
to overflows.h?

Br,

G.G.

On 9/28/22 9:06 PM, Kees Cook wrote:
> On Wed, Sep 28, 2022 at 10:09:04AM -0700, Linus Torvalds wrote:
>> Kees, you need to reign in the craziness in overflow.h.
> 
> Understood. I've been trying to help the drm folks walk a line between
> having a bunch of custom macros hidden away in the drm includes and
> building up generalized versions that are actually helpful beyond drm.
> But I can see that it doesn't help to have a "do two things at the same
> time" macro for the assignment checking.
>