On Sun, Jun 05, 2022 at 04:18:06PM -0700, Jared Kangas wrote:
> gbaudio_dapm_free_controls() iterates over widgets using
> list_for_each_entry_safe(), which leaves the loop cursor pointing to a
> meaningless structure if it completes a traversal of the list. The
> cursor was set to NULL at the end of the loop body, but would be
> overwritten by the final loop cursor update.
>
> Because of this behavior, the widget could be non-null after the loop
> even if the widget wasn't found, and the cleanup logic would treat the
> pointer as a valid widget to free.
>
> To fix this, introduce a temporary variable to act as the loop cursor
> and copy it to a variable that can be accessed after the loop finishes.
>
> This was detected with the help of Coccinelle.
Please add the missing Fixes tag and a CC stable tag here as Dan
mentioned.
> Signed-off-by: Jared Kangas <kangas.jd@xxxxxxxxx>
> ---
> drivers/staging/greybus/audio_helper.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/staging/greybus/audio_helper.c b/drivers/staging/greybus/audio_helper.c
> index 843760675876..07461a5d97c7 100644
> --- a/drivers/staging/greybus/audio_helper.c
> +++ b/drivers/staging/greybus/audio_helper.c
> @@ -115,7 +115,7 @@ int gbaudio_dapm_free_controls(struct snd_soc_dapm_context *dapm,
> int num)
> {
> int i;
> - struct snd_soc_dapm_widget *w, *next_w;
> + struct snd_soc_dapm_widget *w, *next_w, *tmp_w;
> #ifdef CONFIG_DEBUG_FS
> struct dentry *parent = dapm->debugfs_dapm;
> struct dentry *debugfs_w = NULL;
> @@ -124,13 +124,14 @@ int gbaudio_dapm_free_controls(struct snd_soc_dapm_context *dapm,
> mutex_lock(&dapm->card->dapm_mutex);
> for (i = 0; i < num; i++) {
> /* below logic can be optimized to identify widget pointer */
> - list_for_each_entry_safe(w, next_w, &dapm->card->widgets,
> + w = NULL;
> + list_for_each_entry_safe(tmp_w, next_w, &dapm->card->widgets,
This should be list_for_each_entry() as w is not unlinked in this loop.
> list) {
> - if (w->dapm != dapm)
> - continue;
> - if (!strcmp(w->name, widget->name))
> + if (tmp_w->dapm == dapm &&
> + !strcmp(tmp_w->name, widget->name)) {
> + w = tmp_w;
> break;
> - w = NULL;
> + }
> }
> if (!w) {
> dev_err(dapm->dev, "%s: widget not found\n",
Looks good otherwise:
Reviewed-by: Johan Hovold <johan@xxxxxxxxxx>
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