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;
From:   chris hyser <chris.hyser@oracle.com>
To:     chris.hyser@oracle.com, linux-kernel@vger.kernel.org,
        peterz@infradead.org, gregkh@linuxfoundation.org,
        "Rafael J. Wysocki" <rafael@kernel.org>
Subject: [PATCH 1/4] debugfs: return EINVAL if write to unsigned simple files exceed storage.
Date:   Tue, 30 May 2023 15:40:09 -0400
Message-Id: <20230530194012.44411-2-chris.hyser@oracle.com>
In-Reply-To: <20230530194012.44411-1-chris.hyser@oracle.com>
References: <20230530194012.44411-1-chris.hyser@oracle.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?/UtIxtnNRf/QcL92mD0bDAA8sYGGSeAN8qWJ6KRCe66eoA1DGzlI9pHjXk94?=
 =?us-ascii?Q?fkvf15NccpZJb0rGvL2MB+qbQGtMMAYblVltv7xpZbvGWmJI2eAE7SCte4sU?=
 =?us-ascii?Q?h/d6xxZi0ZMmoRscywVq0kI04o5lDtzp2/QAuW67IDGZbwxLuQ4fR4yxjRg6?=
 =?us-ascii?Q?ivCehKHun03bVs8Tir5sj1d6SEvti5GfrUZ2anHZUMO2Rr0gB3nV4uDIpRCh?=
 =?us-ascii?Q?og0/tPJe/6qbIlEZlxDb+FCkJY+QdOgeoViGpJIbSxGTc/AoUDVs5H/WN71g?=
 =?us-ascii?Q?Rym/QyESAl0m/t0CRbH+Iy+NzvZAfPGmCX4SRKonqsfRBqRolplC2s/caC+k?=
 =?us-ascii?Q?Ju45oVUnmKmCH5ndX9Mz0rF7Gx+7mgMHc/qI/uWAl3jkFEYVBbqfchOVgYt1?=
 =?us-ascii?Q?CMW6TRVbwy2P4LoxsM+wZDuGbLQ/poT8veUP/Ee/OtVpjC4JET4m8UeR2V0f?=
 =?us-ascii?Q?U7ri+RDcbQa6nbEYHAiqQINyS4WmM4sUvFbO56i7wpT3kwYyrda5SS20vr9f?=
 =?us-ascii?Q?91KRJFhOo9iX7atGCuou/zm5aRpxI+l8jFbZt2N9HSJgNS21wBkHi7iSsX+9?=
 =?us-ascii?Q?2CO/TeJIuPOr1mrF4FptbVzTnxL5ug5nwjtRc93poGxykW4W02wijGQrP9J7?=
 =?us-ascii?Q?Mg8xSxCGIZJlfjOiyh+hjOrpc6qIgp54hGX+zXQlduHFXSJE9pswJ3yxCwKk?=
 =?us-ascii?Q?JtKA5Kdv+MHcnUEFacDbIknIUe7jl+79I/Xv3ytsRz/oGEOqyp5sANe4qMik?=
 =?us-ascii?Q?lwiZdhayOvp20zGjbZv7YSkr6umI6KJogIdEcWgL6DmefvyPs5TLxSivaEwK?=
 =?us-ascii?Q?22nCENB2amnAXd938+5DghilBUxeuHB2d9bPfofkRqqGkHDFoTUE+RWggGvV?=
 =?us-ascii?Q?7yntwScAWjqn1t+q68riuC6L9x4U4Bdc895SpMZujlDpjsuJHYfglgw15DAg?=
 =?us-ascii?Q?VLO9T4XBWla4du8a0T3nxShJVlsHsPuBW3RHWPPjFjO5KxnNBNrvclIFBDZ+?=
 =?us-ascii?Q?9EA1S4k3DzrLXyroMGV5sU0yv99Fkb133ef7MPb3OnplBCxPyt+vvkaLbxek?=
 =?us-ascii?Q?FV1y6qU2/NmjpO06e1eAyFYhPUfP5LdMcj1MEYrweHS7RUuVtQHJxufkcHRs?=
 =?us-ascii?Q?+AmRuFaEK3HbWoqYqp5BLEzfLhHSTcTCi52maj/YS28JhKTlG29ehhjoh8g6?=
 =?us-ascii?Q?QAeUFa3JEbYc4OIEQvEF+2xpZftdo/uAvV46cyTrv0ayifkxBEw7dzfayFqf?=
 =?us-ascii?Q?g9dCxU9Jn4NzUsCdmq95RdTbpuly7my6DUAXSasIghoXSsluqxPI2Iw2i7/Q?=
 =?us-ascii?Q?no6IKRcE8kNz08THazvHvKbT18OiFadFqgX/FT1v7i+B1vQW7AB0Iu5658te?=
 =?us-ascii?Q?zLhnuKd4OJnRrElyPL0//pHuKs9HOWXiCJN/5+qmrBLbjy+ucuxjzJARxZGH?=
 =?us-ascii?Q?7TLqB086NHen4kSpTWn/yaSytvq4CRHdNC6YdlqttmfOImCmhT18yVJjaAOT?=
 =?us-ascii?Q?KxRcqH44r+3Llq/QmDf7n32zZpuvMLZ8sJFZ8iz1b+JPC93QQN+jfz9HMSwE?=
 =?us-ascii?Q?22JV0IcmgrN96Qwh1SDwiaBkiP4ZrXgvFAO5lgQk?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6e63dd7b-2f66-4e7e-7f9f-08db6145b9ba
X-MS-Exchange-CrossTenant-AuthSource: CO1PR10MB4705.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 May 2023 19:40:30.1077
 (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: vc7Y2KrR1ryH3r96Iy8CS0a0UIYoUHT0DxoGmaR+ZXvGaZqNmyLSpM1eESRlnBPe5+QdPiwVegeiKp7yl/CEaQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR10MB6214
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.176.26
 definitions=2023-05-30_15,2023-05-30_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=999
 adultscore=0 malwarescore=0 bulkscore=0 suspectscore=0 mlxscore=0
 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2304280000 definitions=main-2305300159
X-Proofpoint-GUID: 2a0_VyNLEvLDnDs6A1dJRDvQPPO553oY
X-Proofpoint-ORIG-GUID: 2a0_VyNLEvLDnDs6A1dJRDvQPPO553oY
X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE 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

Writes to the debug files created by "debugfs_create_*" (u8/u16/u32/u64),
(x8/x16/x32/x64) should not silently succeed if the value exceeds the
storage space for the type and upper written bits are lost. Absent an
error, a read should return the last written value.  Current behaviour is
to down cast the storage type thus losing upper bits (thus u64/x64
files are unaffected).

This patch ensures the written value fits into the specified storage space
returning EINVAL on error.

Signed-off-by: Chris Hyser <chris.hyser@oracle.com>
---
 Documentation/filesystems/debugfs.rst | 7 ++++---
 fs/debugfs/file.c                     | 6 ++++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/debugfs.rst b/Documentation/filesystems/debugfs.rst
index dc35da8b8792..6f1ac8d7f108 100644
--- a/Documentation/filesystems/debugfs.rst
+++ b/Documentation/filesystems/debugfs.rst
@@ -85,9 +85,10 @@ created with any of::
 			    struct dentry *parent, u64 *value);
 
 These files support both reading and writing the given value; if a specific
-file should not be written to, simply set the mode bits accordingly.  The
-values in these files are in decimal; if hexadecimal is more appropriate,
-the following functions can be used instead::
+file should not be written to, simply set the mode bits accordingly.  Written
+values that exceed the storage for the type return EINVAL. The values in these
+files are in decimal; if hexadecimal is more appropriate, the following
+functions can be used instead::
 
     void debugfs_create_x8(const char *name, umode_t mode,
 			   struct dentry *parent, u8 *value);
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 1f971c880dde..743ddd04f8d8 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -429,6 +429,8 @@ static struct dentry *debugfs_create_mode_unsafe(const char *name, umode_t mode,
 
 static int debugfs_u8_set(void *data, u64 val)
 {
+	if (val > (1 << sizeof(u8) * 8) - 1)
+		return -EINVAL;
 	*(u8 *)data = val;
 	return 0;
 }
@@ -465,6 +467,8 @@ EXPORT_SYMBOL_GPL(debugfs_create_u8);
 
 static int debugfs_u16_set(void *data, u64 val)
 {
+	if (val > (1 << sizeof(u16) * 8) - 1)
+		return -EINVAL;
 	*(u16 *)data = val;
 	return 0;
 }
@@ -501,6 +505,8 @@ EXPORT_SYMBOL_GPL(debugfs_create_u16);
 
 static int debugfs_u32_set(void *data, u64 val)
 {
+	if (val > (1ull << sizeof(u32) * 8) - 1)
+		return -EINVAL;
 	*(u32 *)data = val;
 	return 0;
 }
-- 
2.31.1