Re: [PATCH v2 1/2] mfd: syscon: add of_syscon_register_regmap() API

["Arnd Bergmann" <arnd@arndb.de>]

On Thu, Jun 20, 2024, at 13:24, Peter Griffin wrote:
> Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
> ---
> Changes in v2:
> - Keep syscon lock held between checking and adding entry (Krzysztof)

Unfortunately you now have a different bug:

> +	/* check if syscon entry already exists */
> +	spin_lock(&syscon_list_slock);
> +
> +	list_for_each_entry(entry, &syscon_list, list)
> +		if (entry->np == np) {
> +			syscon = entry;
> +			break;
> +		}
> +
> +	if (syscon) {
> +		ret = -EEXIST;
> +		goto err_unlock;
> +	}
> +
> +	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
> +	if (!syscon) {
> +		ret = -ENOMEM;
> +		goto err_unlock;
> +	}

You can't use GFP_KERNEL while holding a spinlock.

I think the correct way to do this is to move the allocation
before the locked section, and then free it in the failure case.

     Arnd