On Fri, Jul 16, 2021 at 8:54 AM Len Baker len.baker@gmx.com wrote:
In the rtw_pci_init_rx_ring function the "if (len > TRX_BD_IDX_MASK)" statement guarantees that len is less than or equal to GENMASK(11, 0) or in other words that len is less than or equal to 4095. However the rx_ring->buf has a size of RTK_MAX_RX_DESC_NUM (defined as 512). This way it is possible an out-of-bounds write in the for statement due to the i variable can exceed the rx_ring->buff size.
However, this overflow never happens due to the rtw_pci_init_rx_ring is only ever called with a fixed constant of RTK_MAX_RX_DESC_NUM. But it is better to be defensive in this case and add a new check to avoid overflows if this function is called in a future with a value greater than 512.
Cc: stable@vger.kernel.org
This kinda seems excessive, considering we absolutely know this is not currently a bug. But then, LWN nicely highlighted this thread, which reminds me that even without the Cc stable, this is likely to unnecessarily get picked up:
https://lwn.net/ml/linux-kernel/YO0zXVX9Bx9QZCTs@kroah.com/
And I guess silencing Coverity is a desirable goal in many cases, even if Coverity is being a bit trigger-happy.
So, *shrug*.
Addresses-Coverity-ID: 1461515 ("Out-of-bounds write") Fixes: e3037485c68ec ("rtw88: new Realtek 802.11ac driver") Signed-off-by: Len Baker len.baker@gmx.com
Changelog v1 -> v2
- Remove the macro ARRAY_SIZE from the for loop (Pkshih, Brian Norris).
- Add a new check for the len variable (Pkshih, Brian Norris).
Reviewed-by: Brian Norris briannorris@chromium.org
Thanks.