[PATCH ath-next 2/2] wifi: ath11k: fix overreads in ath11k_wmi_process_csa_switch_count_event()

[Jeff Johnson]

There is no policy entry for WMI_TAG_PDEV_CSA_SWITCH_COUNT_STATUS_EVENT, so
the parse infrastructure does not enforce a minimum length for the event
struct. Additionally, the num_vdevs field is taken directly from firmware
and used as a loop bound over the vdev_ids array without checking that it
fits within the TLV payload. Either condition can cause an out-of-bounds
read.

Add a TLV policy entry for WMI_TAG_PDEV_CSA_SWITCH_COUNT_STATUS_EVENT so
the parse infrastructure enforces a minimum length for the fixed-size event
struct. Add a helper ath11k_wmi_tlv_data_len() to recover the payload
length of a parsed TLV from the header preceding its data pointer. Use it
in ath11k_wmi_process_csa_switch_count_event() to bound num_vdevs before
the loop.

Compile tested only.

Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Jeff Johnson <jeff.johnson at oss.qualcomm.com>
---
 drivers/net/wireless/ath/ath11k/wmi.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/wmi.c b/drivers/net/wireless/ath/ath11k/wmi.c
index dca6e011cc40..feb0a0b29c81 100644
--- a/drivers/net/wireless/ath/ath11k/wmi.c
+++ b/drivers/net/wireless/ath/ath11k/wmi.c
@@ -159,6 +159,8 @@ static const struct wmi_tlv_policy wmi_tlv_policies[] = {
 		.min_len = sizeof(struct ath11k_wmi_p2p_noa_info) },
 	[WMI_TAG_P2P_NOA_EVENT] = {
 		.min_len = sizeof(struct wmi_p2p_noa_event) },
+	[WMI_TAG_PDEV_CSA_SWITCH_COUNT_STATUS_EVENT] = {
+		.min_len = sizeof(struct wmi_pdev_csa_switch_ev) },
 };
 
 #define PRIMAP(_hw_mode_) \
@@ -262,6 +264,13 @@ const void **ath11k_wmi_tlv_parse_alloc(struct ath11k_base *ab,
 	return tb;
 }
 
+static u32 ath11k_wmi_tlv_data_len(const void *data)
+{
+	const struct wmi_tlv *tlv = (const struct wmi_tlv *)data - 1;
+
+	return FIELD_GET(WMI_TLV_LEN, tlv->header);
+}
+
 static int ath11k_wmi_cmd_send_nowait(struct ath11k_pdev_wmi *wmi, struct sk_buff *skb,
 				      u32 cmd_id)
 {
@@ -8353,15 +8362,23 @@ ath11k_wmi_process_csa_switch_count_event(struct ath11k_base *ab,
 					  const struct wmi_pdev_csa_switch_ev *ev,
 					  const u32 *vdev_ids)
 {
-	int i;
+	u32 vdev_ids_len = ath11k_wmi_tlv_data_len(vdev_ids);
+	u32 num_vdevs = ev->num_vdevs;
 	struct ath11k_vif *arvif;
+	int i;
 
 	/* Finish CSA once the switch count becomes NULL */
 	if (ev->current_switch_count)
 		return;
 
+	if (num_vdevs > vdev_ids_len / sizeof(*vdev_ids)) {
+		ath11k_warn(ab, "csa switch count num_vdevs %u exceeds tlv array length %u\n",
+			    num_vdevs, vdev_ids_len);
+		return;
+	}
+
 	rcu_read_lock();
-	for (i = 0; i < ev->num_vdevs; i++) {
+	for (i = 0; i < num_vdevs; i++) {
 		arvif = ath11k_mac_get_arvif_by_vdev_id(ab, vdev_ids[i]);
 
 		if (!arvif) {

-- 
2.43.0