Re: [PATCH v2] wifi: ath9k: hif_usb: fix memory leak of remain_skbs

["Toke Høiland-Jørgensen" <toke@toke.dk>]

Fedor Pchelkin <pchelkin@ispras.ru> writes:

> 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.
>
> Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>

Thank you for the fix!

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>