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Wed, 07 Oct 2026 07:29:00 -0700 (PDT) Received: from linux.tail9b532d.ts.net ([84.75.40.48]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48c71d1272esm5654491f8f.27.2026.10.07.07.28.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Oct 2026 07:28:59 -0700 (PDT) From: Eduard Zateev To: johannes@sipsolutions.net Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, Eduard Zateev , syzbot+d0a52209bddfa0948065@syzkaller.appspotmail.com Subject: [PATCH] wifi: cfg80211: validate WEXT station BSSID Date: Wed, 7 Oct 2026 16:28:55 +0200 Message-ID: <20261007142855.1472524-1-hackerowskiy@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit WEXT IBSS and managed mode store the BSSID in the same wdev->wext.bssid buffer. cfg80211_ibss_wext_siwap() keeps a pointer to that buffer in wext.ibss.bssid. 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