[PATCH v3 5/5] wifi: rsi: fix OOB read from firmware offset field in SDIO RX path

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

The firmware-controlled offset field in rsi_read_pkt() is validated only
when rcv_pkt_len is zero (USB path). For the SDIO path, rcv_pkt_len is
always positive, so the check is skipped entirely. A crafted offset can
cause out-of-bounds reads past the 8192-byte pktbuffer when computing
queue number, length, extended descriptor, and data pointers.

Add a transport-independent bounds check to reject offset values that
exceed the frame's actual_length.

Fixes: dad0d04fa7ba ("rsi: data and management rx path")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Changes in v3:
  - Regenerated from wireless-next with proper git format-patch.

Changes in v2:
  - New patch in v2, not present in v1.

 drivers/net/wireless/rsi/rsi_91x_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/rsi/rsi_91x_main.c b/drivers/net/wireless/rsi/rsi_91x_main.c
index eb950e862ecf1..bc03066a240c1 100644
--- a/drivers/net/wireless/rsi/rsi_91x_main.c
+++ b/drivers/net/wireless/rsi/rsi_91x_main.c
@@ -180,6 +180,12 @@ int rsi_read_pkt(struct rsi_common *common, u8 *rx_pkt, s32 rcv_pkt_len)
 		if (!rcv_pkt_len && offset >
 			RSI_MAX_RX_USB_PKT_SIZE - FRAME_DESC_SZ)
 			goto fail;
+		if (offset > actual_length) {
+			rsi_dbg(ERR_ZONE,
+				"%s: offset %u exceeds length %u\n",
+				__func__, offset, actual_length);
+			goto fail;
+		}
 
 		queueno = rsi_get_queueno(frame_desc, offset);
 		length = rsi_get_length(frame_desc, offset);
-- 
2.47.3