Re: [PATCH] ASoC: meson: Keep link pointers valid on realloc failure

[Jerome Brunet <jbrunet@baylibre.com>]

On jeu. 16 juil. 2026 at 10:25, sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
>
> Pre-existing issues:
> - [High] Unbinding the device causes a use-after-free because `meson_card_remove` frees `card->dai_link` manually before the devres callbacks unregister the card.
> --
>
> --- Patch [1]: [PATCH] ASoC: meson: Keep link pointers valid on realloc failure ---
> commit 677ad75f5fb5a578b984e744f26d24b961c89685
> Author: Linmao Li <lilinmao@kylinos.cn>
>
> ASoC: meson: Keep link pointers valid on realloc failure
>
> This commit fixes a potential use-after-free and double free in the error
> path of meson_card_reallocate_links(). It updates the card->dai_link
> pointer immediately after the first successful krealloc(), ensuring the
> cleanup path can safely free the memory if the second krealloc() fails.
>
>> diff --git a/sound/soc/meson/meson-card-utils.c b/sound/soc/meson/meson-card-utils.c
>> index cdb759b466ad4..38c1b2ae227ff 100644
>> --- a/sound/soc/meson/meson-card-utils.c
>> +++ b/sound/soc/meson/meson-card-utils.c
>> @@ -52,19 +52,18 @@ int meson_card_reallocate_links(struct snd_soc_card *card,
>>  	if (!links)
>>  		goto err_links;
>>  
>> +	priv->card.dai_link = links;
>> +
>>  	ldata = krealloc(priv->link_data,
>>  			 num_links * sizeof(*priv->link_data),
>>  			 GFP_KERNEL | __GFP_ZERO);
>>  	if (!ldata)
>> -		goto err_ldata;
>> +		goto err_links;
>>  
>> -	priv->card.dai_link = links;
>>  	priv->link_data = ldata;
>>  	priv->card.num_links = num_links;
>>  	return 0;
>>  
>> -err_ldata:
>> -	kfree(links);
>>  err_links:
>>  	dev_err(priv->card.dev, "failed to allocate links\n");
>>  	return -ENOMEM;
>
> [Severity: High]
> This isn't a bug introduced by this patch, but does unbinding the device
> cause a use-after-free because meson_card_remove() frees card->dai_link
> manually before the devres callbacks unregister the card?
>
> When the driver is unbound, the driver core calls meson_card_remove(), which
> calls meson_card_clean_references() to free the links:
>
> sound/soc/meson/meson-card-utils.c:meson_card_clean_references() {
>     ...
>     kfree(card->dai_link);
>     ...
> }
>
> Only after .remove returns does the driver core run devres callbacks, which
> includes unregistering the card via devm_snd_soc_register_card's cleanup
> handler.
>
> The ASoC unregister path iterates over all PCM runtimes and dereferences
> rtd->dai_link, which points directly to elements of the already freed
> card->dai_link array.

Indeed. We need to move away from devres card registration to deregister
the card before freeing the rest in the ressource clean up. I'll do so
as soon as we have the v2 of this change.

-- 
Jerome

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