[PATCH wireless v4 3/3] wifi: ath6kl: fix OOB read from firmware num_msg in TX complete handler

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

The firmware-controlled num_msg field (u8, 0-255) drives the loop in
ath6kl_wmi_tx_complete_event_rx() without validation against the buffer
length. This allows out-of-bounds reads of up to 1020 bytes past the
WMI event buffer when the firmware sends an inflated num_msg.

Add a check that the buffer is large enough to hold the fixed struct
and the num_msg variable-length entries.

Fixes: bdcd81707973 ("Add ath6kl cleaned up driver")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Changes in v4:
  - Split combined bounds check into two sequential checks to avoid
    overreading evt->num_msg in the error log when the buffer is too
    small for the fixed struct (Jeff Johnson).

Changes in v3:
  - Regenerated from wireless-next with proper git format-patch to
    produce valid index hashes (v2 had post-processed index lines).

Changes in v2:
  - No code changes from v1.

 drivers/net/wireless/ath/ath6kl/wmi.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/wireless/ath/ath6kl/wmi.c b/drivers/net/wireless/ath/ath6kl/wmi.c
index 3787b9f..a572952 100644
--- a/drivers/net/wireless/ath/ath6kl/wmi.c
+++ b/drivers/net/wireless/ath/ath6kl/wmi.c
@@ -484,6 +484,18 @@ static int ath6kl_wmi_tx_complete_event_rx(u8 *datap, int len)
 
 	evt = (struct wmi_tx_complete_event *) datap;
 
+	if (len < sizeof(*evt)) {
+		ath6kl_dbg(ATH6KL_DBG_WMI, "tx complete: invalid len %d\n",
+			   len);
+		return -EINVAL;
+	}
+
+	if (len < sizeof(*evt) + evt->num_msg * sizeof(struct tx_complete_msg_v1)) {
+		ath6kl_dbg(ATH6KL_DBG_WMI, "tx complete: invalid len %d for %u msgs\n",
+			   len, evt->num_msg);
+		return -EINVAL;
+	}
+
 	ath6kl_dbg(ATH6KL_DBG_WMI, "comp: %d %d %d\n",
 		   evt->num_msg, evt->msg_len, evt->msg_type);
 
-- 
2.47.3