[PATCH ath-next 2/2] wifi: ath12k: fix overflow warning on num_pwr_levels

[Baochen Qiang <baochen.qiang@xxxxxxxxxxxxxxxx>]

From: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>

In ath12k_mac_parse_tx_pwr_env(), for the non-PSD case num_pwr_levels is
limited by ATH12K_NUM_PWR_LEVELS which is 16:

	if (tpc_info->num_pwr_levels > ATH12K_NUM_PWR_LEVELS)
		tpc_info->num_pwr_levels = ATH12K_NUM_PWR_LEVELS;

Then it is used to iterate entries in local_non_psd->power[] and
reg_non_psd->power[]:

	for (i = 0; i < tpc_info->num_pwr_levels; i++) {
		tpc_info->tpe[i] = min(local_non_psd->power[i],
				       reg_non_psd->power[i]) / 2;

Since the two array are of size 5, Smatch warns:

drivers/net/wireless/ath/ath12k/mac.c:9812
ath12k_mac_parse_tx_pwr_env() error: buffer overflow 'local_non_psd->power' 5 <= 15
drivers/net/wireless/ath/ath12k/mac.c:9812
ath12k_mac_parse_tx_pwr_env() error: buffer overflow 'reg_non_psd->power' 5 <= 15

This is a false positive as there is already implicit limitation:

	tpc_info->num_pwr_levels = max(local_non_psd->count,
				       reg_non_psd->count);

meaning it won't exceed 5.

However, to make robot happy, add explicit limit there.

Also add the same to the PSD case, although no warning due to
ATH12K_NUM_PWR_LEVELS equals IEEE80211_TPE_PSD_ENTRIES_320MHZ.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00284-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1

Fixes: cccbb9d0dd6a ("wifi: ath12k: add parse of transmit power envelope element")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Closes: https://lore.kernel.org/r/202505180703.Kr9OfQRP-lkp@xxxxxxxxx/
Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>
---
 drivers/net/wireless/ath/ath12k/mac.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
index 8295480e8b1eeaa3e69cca823e6745733ade50e0..57c81ba988ad3c7c3037286c6c093cef4c4f8116 100644
--- a/drivers/net/wireless/ath/ath12k/mac.c
+++ b/drivers/net/wireless/ath/ath12k/mac.c
@@ -11435,8 +11435,10 @@ static void ath12k_mac_parse_tx_pwr_env(struct ath12k *ar,
 
 		tpc_info->num_pwr_levels = max(local_psd->count,
 					       reg_psd->count);
-		if (tpc_info->num_pwr_levels > ATH12K_NUM_PWR_LEVELS)
-			tpc_info->num_pwr_levels = ATH12K_NUM_PWR_LEVELS;
+		tpc_info->num_pwr_levels =
+				min3(tpc_info->num_pwr_levels,
+				     IEEE80211_TPE_PSD_ENTRIES_320MHZ,
+				     ATH12K_NUM_PWR_LEVELS);
 
 		for (i = 0; i < tpc_info->num_pwr_levels; i++) {
 			tpc_info->tpe[i] = min(local_psd->power[i],
@@ -11451,8 +11453,10 @@ static void ath12k_mac_parse_tx_pwr_env(struct ath12k *ar,
 
 		tpc_info->num_pwr_levels = max(local_non_psd->count,
 					       reg_non_psd->count);
-		if (tpc_info->num_pwr_levels > ATH12K_NUM_PWR_LEVELS)
-			tpc_info->num_pwr_levels = ATH12K_NUM_PWR_LEVELS;
+		tpc_info->num_pwr_levels =
+				min3(tpc_info->num_pwr_levels,
+				     IEEE80211_TPE_EIRP_ENTRIES_320MHZ,
+				     ATH12K_NUM_PWR_LEVELS);
 
 		for (i = 0; i < tpc_info->num_pwr_levels; i++) {
 			tpc_info->tpe[i] = min(local_non_psd->power[i],

-- 
2.25.1