[PATCH v2] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

In rtw_pci_rx_napi(), new_len is computed as the sum of pkt_len (14-bit
descriptor field, max 16383) and pkt_offset (drv_info_sz + shift, both
firmware-controlled). The result can exceed RTK_PCI_RX_BUF_SIZE (11478),
causing an out-of-bounds read from the pre-allocated DMA buffer when
skb_put_data copies new_len bytes. The USB transport already validates
this (rtw_usb_rx_data_put checks against RTW_USB_MAX_RECVBUF_SZ); the
PCIe path does not.

Add a check that new_len does not exceed the DMA buffer size.

Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Note: v2 resubmission -- original sent via Gmail had HTML rendering
issues. This version uses git send-email for plain-text formatting.

Changes in v2:
  - v2: clarify field widths and maximum new_len derivation in commit
    message, per Ping-Ke Shih's feedback.

drivers/net/wireless/realtek/rtw88/pci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -1078,6 +1078,11 @@ static int rtw_pci_rx_napi(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
 		new_len = pkt_stat.pkt_len + pkt_offset;
+		if (new_len > RTK_PCI_RX_BUF_SIZE) {
+			rtw_dbg(rtwdev, RTW_DBG_RX,
+				"oversized RX packet: %u\n", new_len);
+			goto next_rp;
+		}
 		new = dev_alloc_skb(new_len);
 		if (WARN_ONCE(!new, "rx routine starvation\n"))
 			goto next_rp;