CVE-2023-53641wifi: ath9k: hif_usb: fix memory leak of remain_skbs

Official description

In the Linux kernel, the following vulnerability has been resolved: wifi: ath9k: hif_usb: fix memory leak of remain_skbs hif_dev->remain_skb is allocated and used exclusively in ath9k_hif_usb_rx_stream(). It is implied that an allocated remain_skb is processed and subsequently freed (in error paths) only during the next call of ath9k_hif_usb_rx_stream(). So, if the urbs are deallocated between those two calls due to the device deinitialization or suspend, it is possible that ath9k_hif_usb_rx_stream() is not called next time and the allocated remain_skb is leaked. Our local Syzkaller instance was able to trigger that. remain_skb makes sense when receiving two consecutive urbs which are logically linked together, i.e. a specific data field from the first skb indicates a cached skb to be allocated, memcpy'd with some data and subsequently processed in the next call to ath9k_hif_usb_rx_stream(). Urbs deallocation supposedly makes that link irrelevant so we need to free the cached skb in those cases. Fix the leak by introducing a function to explicitly free remain_skb (if it is not NULL) when the rx urbs have been deallocated. remain_skb is NULL when it has not been allocated at all (hif_dev struct is kzalloced) or when it has been processed in next call to ath9k_hif_usb_rx_stream(). Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/6719e3797ec52cd144c8a5ba8aaab36674800585
• https://git.kernel.org/stable/c/d9899318660791141ea6002fda5577b2c5d7386e
• https://git.kernel.org/stable/c/320d760a35273aa815d58b57e4fd9ba5279a3489
• https://git.kernel.org/stable/c/59073060fe0950c6ecbe12bdc06469dcac62128d
• https://git.kernel.org/stable/c/9b9356a3014123f0ce4b50d9278c1265173150ab
• https://git.kernel.org/stable/c/f0931fc8f4b6847c72e170d2326861c0a081d680
• https://git.kernel.org/stable/c/8f02d538878c9b1501f624595eb22ee4e5e0ff84
• https://git.kernel.org/stable/c/7654cc03eb699297130b693ec34e25f77b17c947