wifi: iwlegacy: 4965: fix potential off-by-one overflow in il4965_rs_fill_link_cmd()

As a result of the execution of the inner while loop, the value
of 'idx' can be equal to LINK_QUAL_MAX_RETRY_NUM. However, this
is not checked after the loop and 'idx' is used to write the
LINK_QUAL_MAX_RETRY_NUM size array 'lq_cmd->rs_table[idx]' below
in the outer loop.

The fix is to check the new value of 'idx' inside the nested loop,
and break both loops if index equals the size. Checking it at the
start is now pointless, so let's remove it.

Detected using the static analysis tool - Svace.

Fixes: be663ab6 ("iwlwifi: split the drivers for agn and legacy devices 3945/4965")
Signed-off-by: Alexey Kodanev <aleksei.kodanev@bell-sw.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220608171614.28891-1-aleksei.kodanev@bell-sw.com

drivers/net/wireless/intel/iwlegacy/4965-rs.c

@@ -2403,7 +2403,7 @@ il4965_rs_fill_link_cmd(struct il_priv *il, struct il_lq_sta *lq_sta,
 		/* Repeat initial/next rate.
 		 * For legacy IL_NUMBER_TRY == 1, this loop will not execute.
 		 * For HT IL_HT_NUMBER_TRY == 3, this executes twice. */
-		while (repeat_rate > 0 && idx < LINK_QUAL_MAX_RETRY_NUM) {
+		while (repeat_rate > 0) {
 			if (is_legacy(tbl_type.lq_type)) {
 				if (ant_toggle_cnt < NUM_TRY_BEFORE_ANT_TOGGLE)
 					ant_toggle_cnt++;
@@ -2422,6 +2422,8 @@ il4965_rs_fill_link_cmd(struct il_priv *il, struct il_lq_sta *lq_sta,
 			    cpu_to_le32(new_rate);
 			repeat_rate--;
 			idx++;
+			if (idx >= LINK_QUAL_MAX_RETRY_NUM)
+				goto out;
 		}
 
 		il4965_rs_get_tbl_info_from_mcs(new_rate, lq_sta->band,
@@ -2466,6 +2468,7 @@ il4965_rs_fill_link_cmd(struct il_priv *il, struct il_lq_sta *lq_sta,
 		repeat_rate--;
 	}
 
+out:
 	lq_cmd->agg_params.agg_frame_cnt_limit = LINK_QUAL_AGG_FRAME_LIMIT_DEF;
 	lq_cmd->agg_params.agg_dis_start_th = LINK_QUAL_AGG_DISABLE_START_DEF;