linux-kernel - Re: [PATCH] staging: greybus: audio: fix loop cursor use after iteration

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Date:   Mon, 6 Jun 2022 16:06:26 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Jared Kangas <kangas.jd@...il.com>
Cc:     vaibhav.sr@...il.com, mgreer@...malcreek.com, elder@...nel.org,
        gregkh@...uxfoundation.org, greybus-dev@...ts.linaro.org,
        johan@...nel.org, linux-kernel@...r.kernel.org,
        linux-staging@...ts.linux.dev
Subject: Re: [PATCH] staging: greybus: audio: fix loop cursor use after
 iteration

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.
> 

This needs a Fixes tag.

Fixes: 510e340efe0c ("staging: greybus: audio: Add helper APIs for dynamic audio modules")

Otherwise, looks good!

Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>

regards,
dan carpenter