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

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Message-ID: <5040c16b-7784-42aa-bd2d-ee7e966a924f@sirena.org.uk>
Date: Tue, 4 Mar 2025 13:23:13 +0000
From: Mark Brown <broonie@...nel.org>
To: Zxyan Zhu <zxyan20@....com>
Cc: gregkh@...uxfoundation.org, rafael@...nel.org, dakr@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regmap: debugfs: Fix name collision without atomic
 operations

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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