Re: [PATCH wireless-next] wifi: mac80211: check stations are removed before MLD change

[Ben Greear <greearb@candelatech.com>]

On 5/5/26 06:17, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
> 
> If an interface changes to/from MLD, then all stations related
> to it must have been removed first. This is just natural since
> we go from having links to not (or vice versa), but not doing
> so also causes crashes in debugfs since vif changing to/from
> MLD removes the entire debugfs for the vif, including stations.
> 
> Delete all stations but warn in this case, other code should
> be handling it, in effect fail fast rather than doing a double
> free or use-after-free in debugfs.
> 
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
> ---
> This basically makes sure that the bug I fixed in
> https://lore.kernel.org/linux-wireless/20260505151533.c4e52deb06ad.Iafe56cec7de8512626169496b134bce3a6c17010@changeid/
> is noticed quickly. I'll probably merge this only
> after the fix lands in wireless-next via net/net-next.
> ---
>   net/mac80211/link.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/mac80211/link.c b/net/mac80211/link.c
> index 93e290dd783f..e81dd02de12e 100644
> --- a/net/mac80211/link.c
> +++ b/net/mac80211/link.c
> @@ -2,7 +2,7 @@
>   /*
>    * MLO link handling
>    *
> - * Copyright (C) 2022-2025 Intel Corporation
> + * Copyright (C) 2022-2026 Intel Corporation
>    */
>   #include <linux/slab.h>
>   #include <linux/kernel.h>
> @@ -307,6 +307,9 @@ static int ieee80211_vif_update_links(struct ieee80211_sub_if_data *sdata,
>   	if (old_links == new_links && dormant_links == sdata->vif.dormant_links)
>   		return 0;
>   
> +	if (!old_links || !new_links)
> +		WARN_ON(sta_info_flush(sdata, -1) > 0);

Maybe WARN_ON_ONCE to keep log spam to a minimum?

Thanks,
Ben

> +
>   	/* if there were no old links, need to clear the pointers to deflink */
>   	if (!old_links)
>   		rem |= BIT(0);

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com