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From:   Zheng Wang <zyytlz.wz@163.com>
To:     aspriel@gmail.com
Cc:     franky.lin@broadcom.com, hante.meuleman@broadcom.com,
        kvalo@kernel.org, johannes.berg@intel.com, marcan@marcan.st,
        linus.walleij@linaro.org, jisoo.jang@yonsei.ac.kr,
        linuxlovemin@yonsei.ac.kr, wataru.gohda@cypress.com,
        linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        SHA-cyfmac-dev-list@infineon.com, linux-kernel@vger.kernel.org,
        security@kernel.org, stable@vger.kernel.org,
        hackerzheng666@gmail.com, Zheng Wang <zyytlz.wz@163.com>
Subject: [PATCH v3] brcmfmac: Fix use-after-free bug in  brcmf_cfg80211_detach
Date:   Mon,  6 Nov 2023 12:39:57 +0800
Message-Id: <20231106043957.815407-1-zyytlz.wz@163.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

In brcm80211 driver,it starts with the following invoking chain
to start init a timeout worker:

->brcmf_usb_probe
  ->brcmf_usb_probe_cb
    ->brcmf_attach
      ->brcmf_bus_started
        ->brcmf_cfg80211_attach
          ->wl_init_priv
            ->brcmf_init_escan
              ->INIT_WORK(&cfg->escan_timeout_work,
		  brcmf_cfg80211_escan_timeout_worker);

If we disconnect the USB by hotplug, it will call
brcmf_usb_disconnect to make cleanup. The invoking chain is :

brcmf_usb_disconnect
  ->brcmf_usb_disconnect_cb
    ->brcmf_detach
      ->brcmf_cfg80211_detach
        ->kfree(cfg);

While the timeout woker may still be running. This will cause
a use-after-free bug on cfg in brcmf_cfg80211_escan_timeout_worker.

Fix it by deleting the timer and canceling the worker in
brcmf_cfg80211_detach.

Fixes: e756af5b30b0 ("brcmfmac: add e-scan support.")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Cc: stable@vger.kernel.org
---
v3:
- rename the subject as Johannes suggested
v2:
- fix the error of kernel test bot reported
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
index 667462369a32..646ec8bdf512 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
@@ -8431,6 +8431,9 @@ void brcmf_cfg80211_detach(struct brcmf_cfg80211_info *cfg)
 	if (!cfg)
 		return;
 
+	if (timer_pending(&cfg->escan_timeout))
+		del_timer_sync(&cfg->escan_timeout);
+	cancel_work_sync(&cfg->escan_timeout_work);
 	brcmf_pno_detach(cfg);
 	brcmf_btcoex_detach(cfg);
 	wiphy_unregister(cfg->wiphy);
-- 
2.25.1