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After changing to station mode, cfg80211_mgd_wext_siwap() accepts a multicast AP address and copies it to the buffer. Switching back to IBSS then follows that pointer and uses the multicast address as a fixed BSSID. mac80211 can create a beacon with that address, but cfg80211_get_bss() rejects it, causing WARN_ON(!bss) in cfg80211_ibss_joined() after the join has been reported. Reject invalid station BSSIDs before copying them. A mac80211_hwsim WEXT ioctl test reproduces the reported BSSID and warning; the original syzbot report has no reproducer. Reported-by: syzbot+d0a52209bddfa0948065@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=d0a52209bddfa0948065 Signed-off-by: Eduard Zateev --- net/wireless/wext-sme.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/wireless/wext-sme.c b/net/wireless/wext-sme.c index b5914f3658db..3db73a0765c9 100644 --- a/net/wireless/wext-sme.c +++ b/net/wireless/wext-sme.c @@ -245,6 +245,9 @@ int cfg80211_mgd_wext_siwap(struct net_device *dev, if (is_zero_ether_addr(bssid) || is_broadcast_ether_addr(bssid)) bssid = NULL; + if (bssid && !is_valid_ether_addr(bssid)) + return -EINVAL; + if (wdev->conn) { /* both automatic */ if (!bssid && !wdev->wext.connect.bssid) -- 2.55.0