linux-kernel - [PATCH] wifi: cfg80211: Fix use-after-free bug in brcmf_cfg80211

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Date:   Sat,  4 Nov 2023 13:47:09 +0800
From:   Zheng Wang <zyytlz.wz@....com>
To:     aspriel@...il.com
Cc:     franky.lin@...adcom.com, hante.meuleman@...adcom.com,
        kvalo@...nel.org, johannes.berg@...el.com, marcan@...can.st,
        linus.walleij@...aro.org, jisoo.jang@...sei.ac.kr,
        linuxlovemin@...sei.ac.kr, wataru.gohda@...ress.com,
        linux-wireless@...r.kernel.org,
        brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com, linux-kernel@...r.kernel.org,
        security@...nel.org, stable@...r.kernel.org,
        Zheng Wang <zyytlz.wz@....com>
Subject: [PATCH] wifi: cfg80211: Fix use-after-free bug in brcmf_cfg80211_detach

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@....com>
Cc: stable@...r.kernel.org
---
 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..0224e377eb6e 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_delayed_work_sync(&cfg->escan_timeout_work);
 	brcmf_pno_detach(cfg);
 	brcmf_btcoex_detach(cfg);
 	wiphy_unregister(cfg->wiphy);
-- 
2.25.1