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Fri, 05 Dec 2025 07:35:52 -0800 (PST) Received: from dkarn-thinkpadp16vgen1.punetw6.csb ([2402:e280:3e0d:a45:3861:8b7f:6ae1:6229]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7e2a07213b6sm5641875b3a.26.2025.12.05.07.35.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Dec 2025 07:35:51 -0800 (PST) From: Deepakkumar Karn To: Johannes Berg Cc: Shaul Triebitz , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, Deepakkumar Karn , syzbot+5bb5f06f99924ea0cf86@syzkaller.appspotmail.com Subject: [PATCH] mac80211_hwsim: fix divide error in mac80211_hwsim_link_info_changed Date: Fri, 5 Dec 2025 21:05:02 +0530 Message-ID: <20251205153502.273426-1-dkarn@redhat.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Prevent a division by zero crash when userspace provides a zero beacon interval value. The crash occurs in the beacon timer setup code path when info->beacon_int is 0, causing bcn_int to be 0 and triggering a divide error in the do_div() macro.The issue can be triggered from userspace via nl80211/cfg80211 when configuring a virtual interface in AP mode with an invalid beacon interval. Fixes: e57f8a489c29 ("wifi: mac80211_hwsim: send a beacon per link") Reported-by: syzbot+5bb5f06f99924ea0cf86@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5bb5f06f99924ea0cf86 Signed-off-by: Deepakkumar Karn --- drivers/net/wireless/virtual/mac80211_hwsim.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/net/wireless/virtual/mac80211_hwsim.c b/drivers/net/wireless/virtual/mac80211_hwsim.c index 5903d82e1ab1..e67e2c989ea6 100644 --- a/drivers/net/wireless/virtual/mac80211_hwsim.c +++ b/drivers/net/wireless/virtual/mac80211_hwsim.c @@ -2595,11 +2595,14 @@ static void mac80211_hwsim_link_info_changed(struct ieee80211_hw *hw, link_data->beacon_int = info->beacon_int * 1024; tsf = mac80211_hwsim_get_tsf(hw, vif); bcn_int = link_data->beacon_int; - until_tbtt = bcn_int - do_div(tsf, bcn_int); + /* Proceed only when bcn_int != 0 */ + if (bcn_int) { + until_tbtt = bcn_int - do_div(tsf, bcn_int); - hrtimer_start(&link_data->beacon_timer, - ns_to_ktime(until_tbtt * NSEC_PER_USEC), - HRTIMER_MODE_REL_SOFT); + hrtimer_start(&link_data->beacon_timer, + ns_to_ktime(until_tbtt * NSEC_PER_USEC), + HRTIMER_MODE_REL_SOFT); + } } else if (!info->enable_beacon) { unsigned int count = 0; ieee80211_iterate_active_interfaces_atomic( -- 2.51.1