linux-kernel - [PATCH 4.9 19/42] wifi: mac80211: Dont finalize CSA in IBSS mode if state is disconnected

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Message-Id: <20220913140343.240378340@linuxfoundation.org>
Date:   Tue, 13 Sep 2022 16:07:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+b6c9fe29aefe68e4ad34@...kaller.appspotmail.com,
        Siddh Raman Pant <code@...dh.me>,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 4.9 19/42] wifi: mac80211: Dont finalize CSA in IBSS mode if state is disconnected

From: Siddh Raman Pant <code@...dh.me>

commit 15bc8966b6d3a5b9bfe4c9facfa02f2b69b1e5f0 upstream.

When we are not connected to a channel, sending channel "switch"
announcement doesn't make any sense.

The BSS list is empty in that case. This causes the for loop in
cfg80211_get_bss() to be bypassed, so the function returns NULL
(check line 1424 of net/wireless/scan.c), causing the WARN_ON()
in ieee80211_ibss_csa_beacon() to get triggered (check line 500
of net/mac80211/ibss.c), which was consequently reported on the
syzkaller dashboard.

Thus, check if we have an existing connection before generating
the CSA beacon in ieee80211_ibss_finish_csa().

Cc: stable@...r.kernel.org
Fixes: cd7760e62c2a ("mac80211: add support for CSA in IBSS mode")
Link: https://syzkaller.appspot.com/bug?id=05603ef4ae8926761b678d2939a3b2ad28ab9ca6
Reported-by: syzbot+b6c9fe29aefe68e4ad34@...kaller.appspotmail.com
Signed-off-by: Siddh Raman Pant <code@...dh.me>
Tested-by: syzbot+b6c9fe29aefe68e4ad34@...kaller.appspotmail.com
Link: https://lore.kernel.org/r/20220814151512.9985-1-code@siddh.me
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/mac80211/ibss.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -544,6 +544,10 @@ int ieee80211_ibss_finish_csa(struct iee
 
 	sdata_assert_lock(sdata);
 
+	/* When not connected/joined, sending CSA doesn't make sense. */
+	if (ifibss->state != IEEE80211_IBSS_MLME_JOINED)
+		return -ENOLINK;
+
 	/* update cfg80211 bss information with the new channel */
 	if (!is_zero_ether_addr(ifibss->bssid)) {
 		cbss = cfg80211_get_bss(sdata->local->hw.wiphy,