ath9k: fix use-after-free in ath9k_hif_usb_rx_cb

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ath9k: fix use-after-free in ath9k_hif_usb_rx_cb Syzbot reported use-after-free Read in ath9k_hif_usb_rx_cb() [0]. The problem was in incorrect htc_handle->drv_priv initialization. Probable call trace which can trigger use-after-free: ath9k_htc_probe_device() /* htc_handle->drv_priv = priv; */ ath9k_htc_wait_for_target() <--- Failed ieee80211_free_hw() <--- priv pointer is freed <IRQ> ... ath9k_hif_usb_rx_cb() ath9k_hif_usb_rx_stream() RX_STAT_INC() <--- htc_handle->drv_priv access In order to not add fancy protection for drv_priv we can move htc_handle->drv_priv initialization at the end of the ath9k_htc_probe_device() and add helper macro to make all *_STAT_* macros NULL safe, since syzbot has reported related NULL deref in that macros [1]

References

• https://git.kernel.org/stable/c/62bc1ea5c7401d77eaf73d0c6a15f3d2e742856e
• https://git.kernel.org/stable/c/ab7a0ddf5f1cdec63cb21840369873806fc36d80
• https://git.kernel.org/stable/c/e9e21206b8ea62220b486310c61277e7ebfe7cec
• https://git.kernel.org/stable/c/eccd7c3e2596b574241a7670b5b53f5322f470e5
• https://git.kernel.org/stable/c/03ca957c5f7b55660957eda20b5db4110319ac7a
• https://git.kernel.org/stable/c/6b14ab47937ba441e75e8dbb9fbfc9c55efa41c6
• https://git.kernel.org/stable/c/b66ebac40f64336ae2d053883bee85261060bd27
• https://git.kernel.org/stable/c/0ac4827f78c7ffe8eef074bc010e7e34bc22f533