wifi: iwlegacy: add missing mutex protection in il4965_store_tx_power()

[ Upstream commit e31fa69 ]

il4965_store_tx_power() calls il_set_tx_power() without holding il->mutex.
However, il_set_tx_power() has lockdep_assert_held(&il->mutex) indicating
that callers must hold this lock.

All other callers of il_set_tx_power() properly acquire the mutex:
- il_bg_scan_completed() acquires mutex at common.c:1683
- il_mac_config() acquires mutex at common.c:5006
- il3945_commit_rxon() and il4965_commit_rxon() are called via work
  queues that hold the mutex (like il4965_bg_alive_start)

Add mutex_lock()/mutex_unlock() around the il_set_tx_power() call in
the sysfs store function to fix the missing lock protection.

Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Link: https://patch.msgid.link/20260125194039.1196488-1-n7l8m4@u.northwestern.edu
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: haruki3hhh

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

@@ -4606,7 +4606,9 @@ il4965_store_tx_power(struct device *d, struct device_attribute *attr,
 	if (ret)
 		IL_INFO("%s is not in decimal form.\n", buf);
 	else {
+		mutex_lock(&il->mutex);
 		ret = il_set_tx_power(il, val, false);
+		mutex_unlock(&il->mutex);
 		if (ret)
 			IL_ERR("failed setting tx power (0x%08x).\n", ret);
 		else