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wifi: mac80211: reset state when starting AP fails

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ieee80211_start_ap() can set enable_beacon (and beacon_int) and fail
later, leaving it set forever. Scanning can then attempt to restore
beaconing on such an interface, leading to:

  Oops: divide error: 0000 [#1] SMP KASAN NOPTI
  RIP: 0010:mac80211_hwsim_link_info_changed+0xca7/0xf00
  Call Trace:
   drv_link_info_changed+0x413/0x860 net/mac80211/driver-ops.c:495
   ieee80211_link_info_change_notify+0x24b/0x3c0 net/mac80211/main.c:427
   ieee80211_offchannel_return+0x381/0x580 net/mac80211/offchannel.c:160
   __ieee80211_scan_completed+0x993/0xe30 net/mac80211/scan.c:519
   ieee80211_scan_work+0x472/0x2010 net/mac80211/scan.c:1193
   cfg80211_wiphy_work+0x2b7/0x550 net/wireless/core.c:538

in hwsim. Also, cfg80211 then allows changing the interface type,
and the off-channel path getgs confused about beaconing as well,
leading to another warning:

  WARNING: net/mac80211/driver-ops.c:468 at drv_link_info_changed+0x583/0x880
   ieee80211_link_info_change_notify+0x24b/0x3c0 net/mac80211/main.c:427
   ieee80211_offchannel_stop_vifs+0x328/0x5c0 net/mac80211/offchannel.c:122
   ieee80211_start_sw_scan net/mac80211/scan.c:583 [inline]
   __ieee80211_start_scan+0xfb6/0x1af0 net/mac80211/scan.c:882

Reset the state on failures to always have it correct.

Assisted-by: LLM
Fixes: d6a8322882 ("mac80211: track enable_beacon explicitly")
Reported-by: syzbot+ca7a2759caaa6cd4e3db@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ca7a2759caaa6cd4e3db
Reported-by: syzbot+c4686c3eb8b64032618f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c4686c3eb8b64032618f
Link: https://patch.msgid.link/20260904165722.9629429a5221.I7f599412bfe12a09d41ea4901be9ad165d07d133@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Johannes Berg 2026-09-04 16:57:12 +02:00
parent ac7472a24b
commit 3f28551d02
1 changed files with 3 additions and 0 deletions
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3
net/mac80211/cfg.c
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@ -1929,6 +1929,9 @@ static int ieee80211_start_ap(struct wiphy *wiphy, struct net_device *dev,
return 0;
error:
link_conf->enable_beacon = false;
link_conf->beacon_int = prev_beacon_int;
sdata->vif.cfg.ssid_len = 0;
ieee80211_link_release_channel(link);
return err;