linux-kernel - [PATCH AUTOSEL 6.2 17/17] mtd: spi-nor: fix memory leak when using debugfs

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Message-Id: <20230406113131.648213-17-sashal@kernel.org>
Date:   Thu,  6 Apr 2023 07:31:31 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Pratyush Yadav <pratyush@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, Michael Walle <michael@...le.cc>,
        Sasha Levin <sashal@...nel.org>, tudor.ambarus@...aro.org
Subject: [PATCH AUTOSEL 6.2 17/17] mtd: spi-nor: fix memory leak when using debugfs_lookup()

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

[ Upstream commit ec738ca127d07ecac6afae36e2880341ec89150e ]

When calling debugfs_lookup() the result must have dput() called on it,
otherwise the memory will leak over time.  To solve this, remove the
lookup and create the directory on the first device found, and then
remove it when the module is unloaded.

Cc: Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc: Pratyush Yadav <pratyush@...nel.org>
Cc: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Richard Weinberger <richard@....at>
Cc: Vignesh Raghavendra <vigneshr@...com>
Cc: linux-mtd@...ts.infradead.org
Reviewed-by: Michael Walle <michael@...le.cc>
Link: https://lore.kernel.org/r/20230208160230.2179905-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/mtd/spi-nor/core.c    | 14 +++++++++++++-
 drivers/mtd/spi-nor/core.h    |  2 ++
 drivers/mtd/spi-nor/debugfs.c | 11 ++++++++---
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 2ef2660f58180..4244c6fd98111 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -3344,7 +3344,19 @@ static struct spi_mem_driver spi_nor_driver = {
 	.remove = spi_nor_remove,
 	.shutdown = spi_nor_shutdown,
 };
-module_spi_mem_driver(spi_nor_driver);
+
+static int __init spi_nor_module_init(void)
+{
+	return spi_mem_driver_register(&spi_nor_driver);
+}
+module_init(spi_nor_module_init);
+
+static void __exit spi_nor_module_exit(void)
+{
+	spi_mem_driver_unregister(&spi_nor_driver);
+	spi_nor_debugfs_shutdown();
+}
+module_exit(spi_nor_module_exit);
 
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Huang Shijie <shijie8@...il.com>");
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 958cd143c9346..f4246c52a1def 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -714,8 +714,10 @@ static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)
 
 #ifdef CONFIG_DEBUG_FS
 void spi_nor_debugfs_register(struct spi_nor *nor);
+void spi_nor_debugfs_shutdown(void);
 #else
 static inline void spi_nor_debugfs_register(struct spi_nor *nor) {}
+static inline void spi_nor_debugfs_shutdown(void) {}
 #endif
 
 #endif /* __LINUX_MTD_SPI_NOR_INTERNAL_H */
diff --git a/drivers/mtd/spi-nor/debugfs.c b/drivers/mtd/spi-nor/debugfs.c
index ff895f6758ea1..558ffecf8ae6d 100644
--- a/drivers/mtd/spi-nor/debugfs.c
+++ b/drivers/mtd/spi-nor/debugfs.c
@@ -226,13 +226,13 @@ static void spi_nor_debugfs_unregister(void *data)
 	nor->debugfs_root = NULL;
 }
 
+static struct dentry *rootdir;
+
 void spi_nor_debugfs_register(struct spi_nor *nor)
 {
-	struct dentry *rootdir, *d;
+	struct dentry *d;
 	int ret;
 
-	/* Create rootdir once. Will never be deleted again. */
-	rootdir = debugfs_lookup(SPI_NOR_DEBUGFS_ROOT, NULL);
 	if (!rootdir)
 		rootdir = debugfs_create_dir(SPI_NOR_DEBUGFS_ROOT, NULL);
 
@@ -247,3 +247,8 @@ void spi_nor_debugfs_register(struct spi_nor *nor)
 	debugfs_create_file("capabilities", 0444, d, nor,
 			    &spi_nor_capabilities_fops);
 }
+
+void spi_nor_debugfs_shutdown(void)
+{
+	debugfs_remove(rootdir);
+}
-- 
2.39.2