[PATCH] regmap: debugfs: Fix name collision without atomic operations

[PATCH] regmap: debugfs: Fix name collision without atomic operations

[Zxyan Zhu]

A global variable caused debugfs name conflicts during re-entry,
leading to creation failures. Use atomic operations to ensure safe
and unique naming.

Signed-off-by: Zxyan Zhu <zxyan20@163.com>
---
 drivers/base/regmap/regmap-debugfs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index fb84cda92a75..914fc032861d 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);
@@ -596,11 +596,11 @@ 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);
+						atomic_read(&dummy_index));
 		if (!map->debugfs_name)
 			return;
 		name = map->debugfs_name;
-		dummy_index++;
+		atomic_inc(&dummy_index);
 	}
 
 	map->debugfs = debugfs_create_dir(name, regmap_debugfs_root);
-- 
2.34.1

Re: [PATCH] regmap: debugfs: Fix name collision without atomic operations

[Mark Brown]

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On Tue, Mar 04, 2025 at 08:22:21PM +0800, Zxyan Zhu wrote:

> A global variable caused debugfs name conflicts during re-entry,
> leading to creation failures. Use atomic operations to ensure safe
> and unique naming.

This doesn't help at all AFAICT?  IIRC this code was relying on some
higher level locking but ICBW.

> -						dummy_index);
> +						atomic_read(&dummy_index));

Here we do an atomic read...

>  		if (!map->debugfs_name)
>  			return;
>  		name = map->debugfs_name;
> -		dummy_index++;
> +		atomic_inc(&dummy_index);

...then later we do an atomic increment so something else could also
have come in and done an atomic read before we do the increment.

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Re: [PATCH] regmap: debugfs: Fix name collision without atomic operations

[Greg KH]

On Tue, Mar 04, 2025 at 08:22:21PM +0800, Zxyan Zhu wrote:
> A global variable caused debugfs name conflicts during re-entry,

What global variable?

> leading to creation failures. Use atomic operations to ensure safe
> and unique naming.

Naming of what, the variables or the debugfs file?

confused,

greg k-h