[PATCH v2 2/3] wifi: wcn36xx: fix OOB read from firmware count in PRINT_REG_INFO indication

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

The firmware-controlled rsp->count field is used as the loop bound for
indexing into the flexible rsp->regs[] array without validation against
the message length. A count exceeding the actual data causes out-of-
bounds reads from the heap-allocated message buffer.

Add a check that count fits within the received message.

Fixes: 43efa3c0f241 ("wcn36xx: Implement print_reg indication")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
drivers/net/wireless/ath/wcn36xx/smd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/ath/wcn36xx/smd.c b/drivers/net/wireless/ath/wcn36xx/smd.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/net/wireless/ath/wcn36xx/smd.c
+++ b/drivers/net/wireless/ath/wcn36xx/smd.c
@@ -2803,6 +2803,12 @@ static int wcn36xx_smd_print_reg_info_ind(struct wcn36xx *wcn,
 		return -EIO;
 	}

+	if (rsp->count > (len - sizeof(*rsp)) / sizeof(rsp->regs[0])) {
+		wcn36xx_warn("Truncated print reg info indication: count %u, len %zu\n",
+			     rsp->count, len);
+		return -EIO;
+	}
+
 	wcn36xx_dbg(WCN36XX_DBG_HAL,
 		    "reginfo indication, scenario: 0x%x reason: 0x%x\n",
 		    rsp->scenario, rsp->reason);