[PATCH v2] wifi: mac80211: reject VHT opmode for unsupported channel widths

Moon Hee Lee
2025-07-03T19:38:13Z

VHT operating mode notifications are not defined for channel widths
below 20 MHz. In particular, 5 MHz and 10 MHz are not valid under the
VHT specification and must be rejected.

Without this check, malformed notifications using these widths may
reach ieee80211_chan_width_to_rx_bw(), leading to a WARN_ON due to
invalid input. This issue was reported by syzbot.

Reject these unsupported widths early in sta_link_apply_parameters()
when opmode_notif is used. The accepted set includes 20, 40, 80, 160,
and 80+80 MHz, which are valid for VHT. While 320 MHz is not defined
for VHT, it is allowed to avoid rejecting HE or EHT clients that may
still send a VHT opmode notification.

Reported-by: syzbot+ededba317ddeca8b3f08@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ededba317ddeca8b3f08
Fixes: 751e7489c1d7 ("wifi: mac80211: expose ieee80211_chan_width_to_rx_bw() to drivers")
Tested-by: syzbot+ededba317ddeca8b3f08@syzkaller.appspotmail.com
Signed-off-by: Moon Hee Lee <moonhee.lee.ca@gmail.com>
---
Changes in v2:
- Dropped NL80211_CHAN_WIDTH_20_NOHT from the accepted channel widths.
- Clarified in the commit message that 320 MHz is not defined for VHT
but still allowed to support HE/EHT clients that may send a VHT
opmode notification.

net/mac80211/cfg.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 56540c3701ed..d76643d46150 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1981,6 +1981,20 @@ static int sta_link_apply_parameters(struct ieee80211_local *local,
ieee80211_sta_init_nss(link_sta);

if (params->opmode_notif_used) {
+ enum nl80211_chan_width width = link->conf->chanreq.oper.width;
+
+ switch (width) {
+ case NL80211_CHAN_WIDTH_20:
+ case NL80211_CHAN_WIDTH_40:
+ case NL80211_CHAN_WIDTH_80:
+ case NL80211_CHAN_WIDTH_160:
+ case NL80211_CHAN_WIDTH_80P80:
+ case NL80211_CHAN_WIDTH_320: /* not VHT, allowed for HE/EHT */
+ break;
+ default:
+ return -EINVAL;
+ }
+
/* returned value is only needed for rc update, but the
* rc isn't initialized here yet, so ignore it
*/
--
2.43.0