On Sun, Jul 11, 2021 at 6:43 PM Pkshih pkshih@realtek.com wrote:
-----Original Message----- From: Len Baker [mailto:len.baker@gmx.com]
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.
Fix it using the ARRAY_SIZE macro.
Cc: stable@vger.kernel.org Addresses-Coverity-ID: 1461515 ("Out-of-bounds write")
Coverity seems to be giving a false warning here. I presume it's taking the |len| comparison as proof that |len| might be as large as TRX_BD_IDX_MASK, but as noted below, that's not really true; the |len| comparison is really just dead code.
Fixes: e3037485c68ec ("rtw88: new Realtek 802.11ac driver") Signed-off-by: Len Baker len.baker@gmx.com
To prevent the 'len' argument from exceeding the array size of rx_ring->buff, I suggest to add another checking statement, like
if (len > ARRAY_SIZE(rx_ring->buf)) { rtw_err(rtwdev, "len %d exceeds maximum RX ring buffer\n", len); return -EINVAL; }
That seems like a better idea, if we really need to patch anything.
But, I wonder if this a false alarm because 'len' is equal to ARRAY_SIZE(rx_ring->buf) for now.
Or to the point: rtw_pci_init_rx_ring() is only ever called with a fixed constant -- RTK_MAX_RX_DESC_NUM (i.e., 512) -- so the alleged overflow cannot happen.
Brian