[PATCH v2] wifi: mac80211: mesh: free pending CSA settings on interface stop

[PATCH v2] wifi: mac80211: mesh: free pending CSA settings on interface stop

[Deepanshu Kartikey]

ifmsh->csa is allocated in ieee80211_mesh_csa_beacon() and normally
freed in ieee80211_mesh_finish_csa() once the channel switch
completes. If the mesh interface is stopped while a channel switch
is still in progress, ifmsh->csa is never freed, leaking the
mesh_csa_settings object.

Free it in ieee80211_stop_mesh(), the same way ifmsh->beacon is
already handled there.

Reported-by: syzbot+f5752cd6b94fe38be666@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f5752cd6b94fe38be666
Link: https://lore.kernel.org/all/20260824054611.29728-1-kartikey406@gmail.com/T/ [v1]
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
v2: drop unnecessary NULL check around csa, kfree_rcu() already
    handles a NULL pointer (Nicolas Escande)
---
 net/mac80211/mesh.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index d4507e4e6ec1..48015dcb7add 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -1201,6 +1201,7 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
 	struct ieee80211_local *local = sdata->local;
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 	struct beacon_data *bcn;
+	struct mesh_csa_settings *csa;
 
 	netif_carrier_off(sdata->dev);
 
@@ -1222,6 +1223,11 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
 	RCU_INIT_POINTER(ifmsh->beacon, NULL);
 	kfree_rcu(bcn, rcu_head);
 
+	/* free any pending, unfinished channel switch */
+	csa = sdata_dereference(ifmsh->csa, sdata);
+	RCU_INIT_POINTER(ifmsh->csa, NULL);
+	kfree_rcu(csa, rcu_head);
+
 	/* free all potentially still buffered group-addressed frames */
 	local->total_ps_buffered -= skb_queue_len(&ifmsh->ps.bc_buf);
 	skb_queue_purge(&ifmsh->ps.bc_buf);
-- 
2.34.1

Re: [PATCH v2] wifi: mac80211: mesh: free pending CSA settings on interface stop

[Nicolas Escande]

On Tue Aug 25, 2026 at 3:57 PM CEST, Deepanshu Kartikey wrote:
> ifmsh->csa is allocated in ieee80211_mesh_csa_beacon() and normally
> freed in ieee80211_mesh_finish_csa() once the channel switch
> completes. If the mesh interface is stopped while a channel switch
> is still in progress, ifmsh->csa is never freed, leaking the
> mesh_csa_settings object.
>
> Free it in ieee80211_stop_mesh(), the same way ifmsh->beacon is
> already handled there.
>
> Reported-by: syzbot+f5752cd6b94fe38be666@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=f5752cd6b94fe38be666
> Link: https://lore.kernel.org/all/20260824054611.29728-1-kartikey406@gmail.com/T/ [v1]
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---
> v2: drop unnecessary NULL check around csa, kfree_rcu() already
>     handles a NULL pointer (Nicolas Escande)
> ---
>  net/mac80211/mesh.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
> index d4507e4e6ec1..48015dcb7add 100644
> --- a/net/mac80211/mesh.c
> +++ b/net/mac80211/mesh.c
> @@ -1201,6 +1201,7 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
>  	struct ieee80211_local *local = sdata->local;
>  	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
>  	struct beacon_data *bcn;
> +	struct mesh_csa_settings *csa;
>  
>  	netif_carrier_off(sdata->dev);
>  
> @@ -1222,6 +1223,11 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
>  	RCU_INIT_POINTER(ifmsh->beacon, NULL);
>  	kfree_rcu(bcn, rcu_head);
>  
> +	/* free any pending, unfinished channel switch */
> +	csa = sdata_dereference(ifmsh->csa, sdata);
> +	RCU_INIT_POINTER(ifmsh->csa, NULL);
> +	kfree_rcu(csa, rcu_head);
> +
>  	/* free all potentially still buffered group-addressed frames */
>  	local->total_ps_buffered -= skb_queue_len(&ifmsh->ps.bc_buf);
>  	skb_queue_purge(&ifmsh->ps.bc_buf);

Reviewed-by: Nicolas Escande <nico.escande@gmail.com>