Re: [PATCH] wifi: ath12k: fix channel list double-free on error paths

[Baochen Qiang <baochen.qiang@oss.qualcomm.com>]

On 7/31/2026 5:38 PM, Linkai Gong wrote:
> ath12k_mac_setup_channels_rates() frees band channel arrays on failure
> but either leaves the pointers non-NULL or clears the wrong band. Later
> ath12k_mac_cleanup_unregister() frees the same pointers again.

The radio that frees its sbands[].channels inside setup_channels_rates() is precisely the
one excluded from cleanup_unregister() — the loop is for (j = 0; j < i; j++) and the
failing radio is index i. The earlier radios (0..i-1) all fully succeeded, so their
channel arrays are valid and freed exactly once. So this is actually a dangling pointer
issue, not a reachable double-free — nothing frees the failing radio's pointers a second
time. Please reword the message to something like "error paths leave dangling pointers + a
copy-paste typo; harden by consistently nulling after kfree()."

> 
> Clear the correct sbands[].channels pointers after kfree(), including
> a copy-paste bug that nulled 2 GHz after freeing 6 GHz channels.
> 
> Fixes: acc152f9be20 ("wifi: ath12k: combine channel list for split-phy devices in single-wiphy")
> Signed-off-by: Linkai Gong <gonglinkai@kylinos.cn>
> ---
>  drivers/net/wireless/ath/ath12k/mac.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
> index a0928890671a..5468a8d2d5d5 100644
> --- a/drivers/net/wireless/ath/ath12k/mac.c
> +++ b/drivers/net/wireless/ath/ath12k/mac.c
> @@ -14275,6 +14275,7 @@ static int ath12k_mac_setup_channels_rates(struct ath12k *ar,
>  					   sizeof(ath12k_6ghz_channels), GFP_KERNEL);
>  			if (!channels) {
>  				kfree(ar->mac.sbands[NL80211_BAND_2GHZ].channels);
> +				ar->mac.sbands[NL80211_BAND_2GHZ].channels = NULL;
>  				return -ENOMEM;
>  			}
>  
> @@ -14325,7 +14326,9 @@ static int ath12k_mac_setup_channels_rates(struct ath12k *ar,
>  					   GFP_KERNEL);
>  			if (!channels) {
>  				kfree(ar->mac.sbands[NL80211_BAND_2GHZ].channels);
> +				ar->mac.sbands[NL80211_BAND_2GHZ].channels = NULL;
>  				kfree(ar->mac.sbands[NL80211_BAND_6GHZ].channels);
> +				ar->mac.sbands[NL80211_BAND_6GHZ].channels = NULL;
>  				return -ENOMEM;
>  			}
>  
> @@ -14365,7 +14368,7 @@ static int ath12k_mac_setup_channels_rates(struct ath12k *ar,
>  					kfree(ar->mac.sbands[NL80211_BAND_2GHZ].channels);
>  					ar->mac.sbands[NL80211_BAND_2GHZ].channels = NULL;
>  					kfree(ar->mac.sbands[NL80211_BAND_6GHZ].channels);
> -					ar->mac.sbands[NL80211_BAND_2GHZ].channels = NULL;
> +					ar->mac.sbands[NL80211_BAND_6GHZ].channels = NULL;
>  					kfree(channels);
>  					band->channels = NULL;
>  					return ret;

actual code change looks good