CVE-2024-35811: Use After Free

In the Linux kernel, the following vulnerability has been resolved:

wifi: brcmfmac: Fix use-after-free bug in brcmf_cfg80211_detach

This is the candidate patch of CVE-2023-47233 : https://nvd.nist.gov/vuln/detail/CVE-2023-47233

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.

[[email protected]: keep timer delete as is and cancel work just before free]