On 6/24/2025 9:35 PM, Johannes Berg wrote:
- Remove WARN_ON and early return in ieee80211_report_disconnect()
- Change the return type of ieee80211_set_disassoc(). If
ieee80211_report_disconnect() uses the frame_buf initialized by
ieee80211_set_disassoc(), its invocation is now conditional based
on the return value of ieee80211_set_disassoc().
I don't understand this change ... surely syzbot couldn't have run into
an uninitialized buffer after the WARN_ON since it has panic_on_warn. So
why all these changes:
yes, syzbot couldn't have run into an uninitialized buffer after the
WARN_ON on **patch v2** such as:
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -4433,6 +4433,10 @@ static void ieee80211_report_disconnect(struct
ieee80211_sub_if_data *sdata,
.u.mlme.data = tx ? DEAUTH_TX_EVENT : DEAUTH_RX_EVENT,
.u.mlme.reason = reason,
};
+ struct sta_info *ap_sta = sta_info_get(sdata, sdata->vif.cfg.ap_addr);
+
+ if (WARN_ON(!ap_sta))
+ return;
I think you misunderstood ... We have this WARN_ON since 687a7c8a7227
("wifi: mac80211: change disassoc sequence a bit"). Therefore, !ap_sta
cannot be the cause of syzbot complaints, since WARN_ON would panic it
In my experience, WARN_ON is rarely configured to trigger a panic.
before it ever gets to the uninitialized memory use.
Hi johannes
Thanks a lot for your discussion and review~
>>>
We have this WARN_ON since 687a7c8a7227
("wifi: mac80211: change disassoc sequence a bit")
>>>
this WARN_ON was added in func ieee80211_set_disassoc() but not
ieee80211_report_disconnect()
I add WARN_ON on ieee80211_report_disconnect() on my patch v2,
It was precisely because of the WARN_ON at 687a7c8a7227 that caused
ieee80211_set_disassoc to return early(when panic_on_warn is not
enabled). As a result, ieee80211_set_disassoc failed to properly
initialize frame_buf. Then, when ieee80211_report_disconnect was called,
it ended up using an uninitialized value.
"You're adding a WARN_ON() that's now guaranteed to trigger, no
so now it's no longer your WARN_ON, I guess, but how did it trigger? I
really think we need to figure out how it triggered and fix _that_.
The bug was triggered as follow:
Commit 687a7c8a7227 ("wifi: mac80211: change disassoc sequence a bit")
introduced a code path where ieee80211_set_disassoc may return early if
WARN_ON(!ap_sta) is triggered(panic_on_warn is not enabled). In this
case, frame_buf is not initialized.
Later, when ieee80211_report_disconnect is called, it attempts to use
the uninitialized frame_buf, resulting in a bug.
This is the reason I tagged:
Fixes: 687a7c8a7227 ("wifi: mac80211: change disassoc sequence a bit")
In my patch v2, I want to fix the bug by adding "WARN_ON(!ap_sta) and
return" on ieee80211_report_disconnect() to avoid continue use frame_buf.
In my patch v3, I plan to fix the bug by avoid calling
ieee80211_report_disconnect() when frame_buf is not initialized by
ieee80211_set_disassoc()
johannes
--
Thx and BRs,
Zhongqiu Han
