wifi: iwlwifi: mvm: fix 6 GHz scan construction

If more than 255 colocated APs exist for the set of all
APs found during 2.4/5 GHz scanning, then the 6 GHz scan
construction will loop forever since the loop variable
has type u8, which can never reach the number found when
that's bigger than 255, and is stored in a u32 variable.
Also move it into the loops to have a smaller scope.

Using a u32 there is fine, we limit the number of APs in
the scan list and each has a limit on the number of RNR
entries due to the frame size. With a limit of 1000 scan
results, a frame size upper bound of 4096 (really it's
more like ~2300) and a TBTT entry size of at least 11,
we get an upper bound for the number of ~372k, well in
the bounds of a u32.

Cc: [email protected]
Fixes: eae94cf ("iwlwifi: mvm: add support for 6GHz")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219375
Link: https://patch.msgid.link/20241023091744.f4baed5c08a1.I8b417148bbc8c5d11c101e1b8f5bf372e17bf2a7@changeid
Signed-off-by: Johannes Berg <[email protected]>

Author: jmberg-intel

drivers/net/wireless/intel/iwlwifi/mvm/scan.c

@@ -1774,7 +1774,7 @@ iwl_mvm_umac_scan_cfg_channels_v7_6g(struct iwl_mvm *mvm,
 			&cp->channel_config[ch_cnt];
 
 		u32 s_ssid_bitmap = 0, bssid_bitmap = 0, flags = 0;
-		u8 j, k, n_s_ssids = 0, n_bssids = 0;
+		u8 k, n_s_ssids = 0, n_bssids = 0;
 		u8 max_s_ssids, max_bssids;
 		bool force_passive = false, found = false, allow_passive = true,
 		     unsolicited_probe_on_chan = false, psc_no_listen = false;
@@ -1799,7 +1799,7 @@ iwl_mvm_umac_scan_cfg_channels_v7_6g(struct iwl_mvm *mvm,
 		cfg->v5.iter_count = 1;
 		cfg->v5.iter_interval = 0;
 
-		for (j = 0; j < params->n_6ghz_params; j++) {
+		for (u32 j = 0; j < params->n_6ghz_params; j++) {
 			s8 tmp_psd_20;
 
 			if (!(scan_6ghz_params[j].channel_idx == i))
@@ -1873,7 +1873,7 @@ iwl_mvm_umac_scan_cfg_channels_v7_6g(struct iwl_mvm *mvm,
 		 * SSID.
 		 * TODO: improve this logic
 		 */
-		for (j = 0; j < params->n_6ghz_params; j++) {
+		for (u32 j = 0; j < params->n_6ghz_params; j++) {
 			if (!(scan_6ghz_params[j].channel_idx == i))
 				continue;