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;
Date:   Thu, 6 Apr 2023 18:04:37 -0400
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-next@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] mm/mprotect: Fix do_mprotect_pkey() return on error
Message-ID: <20230406220437.wiks6gm3k6tt662f@revolver>
Mail-Followup-To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-next@vger.kernel.org,
        stable@vger.kernel.org
References: <20230406193050.1363476-1-Liam.Howlett@oracle.com>
 <20230406145345.9c5e4c91461cbf42509a92a9@linux-foundation.org>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230406145345.9c5e4c91461cbf42509a92a9@linux-foundation.org>
User-Agent: NeoMutt/20220429
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?25Poy6t76GkxnmFmcvuZW00rPXUdatc1gWFugL3PQez9CXoaA86l0VqfryRV?=
 =?us-ascii?Q?ae/VAHuWHH8fkT90ucEz9cm3IVACzLvNYHRD2abx1HO2slw/gHzmkEh1vFr/?=
 =?us-ascii?Q?FjEvT2vwjV7Lt8vjnCqshcEJKBPTzgjGVJRYHkRXPjpvUnOUS8StgHBSbzox?=
 =?us-ascii?Q?CQEySgJyRQTPo+bqPMzXOs1pXslzjCVmlJRLgfCLv57CJQV+arQq5KWbfc+S?=
 =?us-ascii?Q?SH5Fq04ZSu7Bjk2Y7XZqYFFtiDck4JlLGfgaLjX4zdFU3O7ooPVLYJYR8955?=
 =?us-ascii?Q?w4WMqh9na9ux9zB/dSJV6tIpA3klkMw6cyGRY7VL6F2GQsvUMmdaYyl+5f2U?=
 =?us-ascii?Q?K2JJNJ+woWeZhwN9RWB606hndWwaJ6TcyZMVaTXdvr2e2QM7tzbPvcwBJOjS?=
 =?us-ascii?Q?t+jwrrx8aRIAGXbf8cRQzyRyWVpioPJvcYIcdyQVegggo3k7ZKd6FsGf+hh1?=
 =?us-ascii?Q?BWV/C0UiOT6FvMeCW/aTR64UEdF5Ae+0Mx2NWn2GojYECksFduz/WL4ZndME?=
 =?us-ascii?Q?AOaUbEFsd2FyOCMCxhS4NTE6g7pZ4oQT0Ps0sBp1km76qT70SbhVqkBt9XjY?=
 =?us-ascii?Q?/SLI1gFKtJRySNYOdEr4FYl9XfpM69q6/kkNR1PXgFYg4ShXK80pM46DFdTq?=
 =?us-ascii?Q?lIfmntWhPy7ewkJi3Hu5iMJjKfaQB2ywwq9vudSmewT/sVvzu+h9rVBHmmIG?=
 =?us-ascii?Q?lTd35vwZmJF+C3hWQNcSwBwzQmZeQmMhdtKM2eTMl+wUNiuLit/3+6sXFI5s?=
 =?us-ascii?Q?0HXND514UAcSMkaUX56XSRkMR5VlxKfpJaEExOWaFsADyIpbPrkT50rimh7o?=
 =?us-ascii?Q?GVD0swbRzvStB/XIObLns8rq9awLfXl60XcS5X6ApzbPgaFp91BocQ/PvkJ7?=
 =?us-ascii?Q?/O1efoXy9YQfz3WkGpmwQSA5d8RF9g4VK9NxkZAq+gza41+kcAW7xm6gP/Fa?=
 =?us-ascii?Q?1GJM7fzbbcK1AiBmdjrE5V3hUi3vlGZey07iy1nkZtaFj1kqI8/4glVNCWjG?=
 =?us-ascii?Q?13Doebyyz6fmKFolXzVWGi1bR5BajHDbvV0u7Th0/4aZJ3PvDnMwndHfEArS?=
 =?us-ascii?Q?n2JAifFuRFloCHnXLaU7ubAaJtEK0PRKkWvoC5TFlGg/iLB3FLJI/3RhkA72?=
 =?us-ascii?Q?BK8Nlisv/gfEUZIOgGHSufdG1rz7Woo5OODs783QT1g/LiHdzbssm5wKm/aI?=
 =?us-ascii?Q?51K7Ix9A2SmttrperaHMVD7dVdRXJdvQ/jIz0BXjc0r4lKWUejs/qqhT8riG?=
 =?us-ascii?Q?AeMXTXKxdssU2OLtsY7RcDhASE9b9r/3dnV+zodm2g00auqSRSSvy0BTyboj?=
 =?us-ascii?Q?IjvHp8W7/azA0J4Qk7B4SsnRmPl31ZLQuS5g7b1qZ5n9NgYGTVnJzkMpf8vy?=
 =?us-ascii?Q?S8oJHoIqagj+r+dVm+DdytGbKN5ra3vdbrUnRK5OAno59rSRzoYkRUGbrLdv?=
 =?us-ascii?Q?NkE+vU3buyXjCT+a4KuFlsnulWftuc50pnIWZjhhnIk6h+KSuEHkwhE7sY97?=
 =?us-ascii?Q?dfmCqwTMI2Foyb8jUMj/fD5Swgv5UP4F5KmnK5OnR3be90xbvsDpAyRf+72P?=
 =?us-ascii?Q?J1j8yEfcIzUb3jsBAXoK2oZGTCcvbTOP03ZounLzzVz44o8qOtGBMOD1pfLR?=
 =?us-ascii?Q?gQ=3D=3D?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: WEA/pb1FvbIYMM/WBeBBsQxx/up6VAopb8eDIPH8banVoj/x+X5z0T+fqpMyMlJxZwfv3W4TZlcZ3oJR1GDz6mTStoZQOiofJjinafbOMVhSzERAzltP357E9lSfiCHuIb4B0dcnjC7Z1gO6DHJh6LRLjna+ayEgUVhl9XQaSvZqpZzvpOVHVSqW2z5BoprGv4UPbxTk/8aWvONxTrtJFvC+OX9L2aEPGuvv9VIZigc69GLrixWjSvDj1+/eyshamqgeNXaPJOLx8c4Er/ugeGN93FGfAYoupc6fBWOt5RcNVE32TYN5oASQGmh7A32hJOKuciPW5S0XmChnrih34XRKu+h2r58U8fB4yWHOvTjfwQvf794Njje4Nne5RGsIa49SBbOUmkShVNouw7FZS9eJ0KV+8CXsBLxqtm/vZ+PvL70fB7j02owns5PYNOTwzKh12qroA12RbQBxsEjxoQqbrWiS5Rja+/qw8kHyB20il9ouuD0X4LWHHyuMpPExaeoR2ZGrdwXBxtQx+FtZ6ED05hJc1r368KSCUPSQ5TrSDsPgVxymcN8dLum3gegfgdRLgrfF7hhD7QPLmJyOJwOyLEnS14g/m95H0wGm6MKsHgAFyNcDsjhGaAg9EdpZQvyuP+Pnyl+ymdmpU9iOfbCPfuYw08K1EihnG0Cx/y8PKfhUc5pSg5qz2RJZoZ+5NCAnzuGUitYxiOcqHSFRneTz9F2W3j4HV42seztvbP87E3Vmx2kwFrM0R3FUN1oJTHB7S1sUjaLwI44xQv6ccJzfiw8xcRJoRSwIENfWC1+TVo7/NPHo+zy/mwMbjr7vIYVUVEqQJ0lkG8jUzwgW1g==
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: ba6313dd-952b-4723-e5fd-08db36eaebd7
X-MS-Exchange-CrossTenant-AuthSource: SN6PR10MB3022.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Apr 2023 22:04:41.1179
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: dI1Oz0pSUiDJx7631AckZkhIMQXO7mr306OsUbNW306bscqLMXGzJmwli3BsPKWs2XJmDqYDKZBpdtDBcBoNgg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BLAPR10MB4882
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22
 definitions=2023-04-06_12,2023-04-06_03,2023-02-09_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxscore=0 malwarescore=0
 mlxlogscore=999 adultscore=0 phishscore=0 suspectscore=0 bulkscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2303200000
 definitions=main-2304060195
X-Proofpoint-ORIG-GUID: F6VNwk1f5u0sRS0NwFp_q6-2xgxQ4hAs
X-Proofpoint-GUID: F6VNwk1f5u0sRS0NwFp_q6-2xgxQ4hAs
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
        DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H2,
        SPF_HELO_NONE,SPF_NONE autolearn=unavailable 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

* Andrew Morton <akpm@linux-foundation.org> [230406 17:53]:
> On Thu,  6 Apr 2023 15:30:50 -0400 "Liam R. Howlett" <Liam.Howlett@oracle.com> wrote:
> 
> > When the loop over the VMA is terminated early due to an error, the
> > return code could be overwritten with ENOMEM.  Fix the return code by
> > only setting the error on early loop termination when the error is not
> > set.
> > 
> > Fixes: 2286a6914c77 ("mm: change mprotect_fixup to vma iterator")
> > Cc: <stable@vger.kernel.org>
> 
> I do think we should always describe the user-visible effects when
> proposing a backport.
> 
> a) so the -stable maintainers understand why we're recommending the
>    backport and
> 
> b) to help some poor soul who is looking at the patch wondering if
>    it will fix his customer's bug report.

Thanks, I'll keep this in mind.

> 
> How's this?
> 
> : User-visible effects include: attempts to run mprotect() against a special
> : mapping or with a poorly-aligned hugetlb address should return -EINVAL,
> : but they presently return -ENOMEM.

That sounds reasonable, although this isn't an exhaustive list. It could
be an -EACCESS for multiple reasons, or anything the vm_ops returns.