If an interface is changed to AP mode but not started, its channel context configuration (chanctx_conf) remains NULL. If a station is then added to this interface, the kernel may automatically set the NL80211_STA_FLAG_ASSOCIATED flag for compatibility with older userspace applications. When this flag is set, sta_apply_auth_flags() attempts to initialize rate control for the station by calling rate_control_rate_init_all_links(). This eventually leads to rate_control_rate_init(), which dereferences the NULL chanctx_conf, triggering a WARN_ON: WARNING: net/mac80211/rate.c:51 at rate_control_rate_init+0x5a6/0x630 ... Call Trace: rate_control_rate_init_all_links+0xf4/0x190 net/mac80211/rate.c:84 sta_apply_auth_flags+0x1bc/0x430 net/mac80211/cfg.c:2152 sta_apply_parameters+0x126d/0x1b10 net/mac80211/cfg.c:2618 ieee80211_add_station+0x3de/0x700 net/mac80211/cfg.c:2684 rdev_add_station+0xfc/0x290 net/wireless/rdev-ops.h:201 nl80211_new_station+0x1b4e/0x1fd0 net/wireless/nl80211.c:9505 Fix this by rejecting the addition or modification of a station to the associated state if the AP has not been started (chanctx_conf is NULL). Exempt Multi-Link Operation (MLO) interfaces from this check, as they handle chanctx_conf per-link rather than globally on the VIF. Fixes: 55de908ab292 ("mac80211: use channel contexts") Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview syzbot Reported-by: syzbot+9bdc0c5998ab45b05030@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9bdc0c5998ab45b05030 Link: https://syzkaller.appspot.com/ai_job?id=0c474d56-8871-480a-8ac4-9a9658930b46 To: "Johannes Berg" To: Cc: --- v3: - Added an empty line after the newly added code block for better readability. v2: - Moved the chanctx_conf check inside the WLAN_STA_RATE_CONTROL check block. - Removed a phrase from the commit description as requested by reviewers. https://lore.kernel.org/all/79cbf145-6652-4e15-be67-f7974ebc29cb@mail.kernel.org/T/ v1: https://lore.kernel.org/all/8e8a5122-a09e-43b2-b42f-4c73b021b173@mail.kernel.org/T/ --- diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index 3b58af59f..d4331fbae 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -2148,8 +2148,14 @@ static int sta_apply_auth_flags(struct ieee80211_local *local, * well. Some drivers require rate control initialized * before drv_sta_state() is called. */ - if (!test_sta_flag(sta, WLAN_STA_RATE_CONTROL)) + if (!test_sta_flag(sta, WLAN_STA_RATE_CONTROL)) { + if (!ieee80211_vif_is_mld(&sta->sdata->vif) && + !rcu_access_pointer( + sta->sdata->vif.bss_conf.chanctx_conf)) + return -EINVAL; + rate_control_rate_init_all_links(sta); + } ret = sta_info_move_state(sta, IEEE80211_STA_ASSOC); if (ret) base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 -- This is an AI-generated patch subject to moderation. Reply with '#syz upstream' to Sign-off the patch as a human author and send it to the upstream kernel mailing lists. Reply with '#syz reject' to reject it ('#syz unreject' to undo). See https://goo.gle/syzbot-ai-patches for information about AI-generated patches. You can comment on the patch as usual, syzbot will try to address the comments and send a new version of the patch if necessary. syzbot engineers can be reached at syzkaller@googlegroups.com.