linux-kernel - [PATCH v2] regmap: debugfs: Fix name collision without atomic operations

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Message-Id: <20250304142452.3521828-1-zxyan20@163.com>
Date: Tue,  4 Mar 2025 22:24:52 +0800
From: Zxyan Zhu <zxyan20@....com>
To: broonie@...nel.org
Cc: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	dakr@...nel.org,
	linux-kernel@...r.kernel.org,
	Zxyan Zhu <zxyan20@....com>
Subject: [PATCH v2] regmap: debugfs: Fix name collision without atomic operations

The `dummy_index` global variable caused debugfs file name conflicts
during re-entry, leading to creation failures. Use atomic operations
to ensure safe and unique debugfs `dummy%d` naming.

Changes since v1:
- Replaced atomic_read + atomic_inc with atomic_inc_return.
- Added atomic_dec in the error path to maintain index consistency.
- Updated the commit message to clarify the fix.

Signed-off-by: Zxyan Zhu <zxyan20@....com>
---
 drivers/base/regmap/regmap-debugfs.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index fb84cda92a75..60c8d9a673b8 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -20,7 +20,7 @@ struct regmap_debugfs_node {
 	struct list_head link;
 };
 
-static unsigned int dummy_index;
+static atomic_t dummy_index = ATOMIC_INIT(0);
 static struct dentry *regmap_debugfs_root;
 static LIST_HEAD(regmap_debugfs_early_list);
 static DEFINE_MUTEX(regmap_debugfs_early_lock);
@@ -549,6 +549,7 @@ void regmap_debugfs_init(struct regmap *map)
 	struct regmap_range_node *range_node;
 	const char *devname = "dummy";
 	const char *name = map->name;
+	int index;
 
 	/*
 	 * Userspace can initiate reads from the hardware over debugfs.
@@ -595,12 +596,13 @@ void regmap_debugfs_init(struct regmap *map)
 
 	if (!strcmp(name, "dummy")) {
 		kfree(map->debugfs_name);
-		map->debugfs_name = kasprintf(GFP_KERNEL, "dummy%d",
-						dummy_index);
-		if (!map->debugfs_name)
+		index = atomic_inc_return(&dummy_index);
+		map->debugfs_name = kasprintf(GFP_KERNEL, "dummy%d", index);
+		if (!map->debugfs_name) {
+			atomic_dec(&dummy_index);
 			return;
+		}
 		name = map->debugfs_name;
-		dummy_index++;
 	}
 
 	map->debugfs = debugfs_create_dir(name, regmap_debugfs_root);
-- 
2.34.1