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

On jeu. 16 juil. 2026 at 18:09, Linmao Li <[email protected]> wrote:

> meson_card_reallocate_links() grows the DAI link and private data
> arrays with two consecutive krealloc() calls and updates the owner
> pointers only after both calls have succeeded.
>
> A successful krealloc() may move the data: it frees the old block and
> returns a new one. When that happens for the link array and the second
> krealloc() then fails, card->dai_link still points to the block that
> krealloc() already freed, and the error path frees the new block too.
> The probe error path then calls meson_card_clean_references(), which
> dereferences card->dai_link and kfree()s it again, resulting in a
> use-after-free and a double free.
>
> Set card->dai_link right after the first krealloc() succeeds and keep
> the resized array when the second call fails, so the pointer always
> refers to a valid allocation that the normal cleanup path can free.
> card->num_links is still updated only on full success, which keeps the
> cleanup limited to initialized links.
>
> Fixes: 7864a79f37b5 ("ASoC: meson: add axg sound card support")
> Signed-off-by: Linmao Li <[email protected]>

Thanks for this

With this fix there is not much point in keeping the labels doing the
goto error handling. Please remove those (and the err print) and just return
-ENOMEM.

> ---
>  sound/soc/meson/meson-card-utils.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/sound/soc/meson/meson-card-utils.c b/sound/soc/meson/meson-card-utils.c
> index cdb759b466ad..38c1b2ae227f 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;

You must assign num_links too for this to be consistent.

> +
>  	ldata = krealloc(priv->link_data,
>  			 num_links * sizeof(*priv->link_data),
>  			 GFP_KERNEL | __GFP_ZERO);
>  	if (!ldata)

Adding a comment here saying that meson_card_clean_references() will
take care of the above on the exist path would be helpful

> -		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;

With this

Reviewed-by: Jerome Brunet <[email protected]>

-- 
Jerome

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