msm: ipa3: add lock for num_q6_rule

There is a race condition be observed
on global variable num_q6_rule used in
ipa wan-driver. The fix is to add lock
to prevent different threads are accessing
it at the same time.

Bug: 68992477
Change-Id: Ia9190c60361cb5605b61963309beca3acdeac89d
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>

drivers/platform/msm/ipa/rmnet_ipa.c

@@ -375,12 +375,15 @@ int copy_ul_filter_rule_to_ipa(struct ipa_install_fltr_rule_req_msg_v01
 {
 	int rc = 0, i, j;
 
+	/* prevent multi-threads accessing num_q6_rule */
+	mutex_lock(&add_mux_channel_lock);
 	if (rule_req->filter_spec_list_valid == true) {
 		num_q6_rule = rule_req->filter_spec_list_len;
 		IPAWANDBG("Received (%d) install_flt_req\n", num_q6_rule);
 	} else {
 		num_q6_rule = 0;
 		IPAWANERR("got no UL rules from modem\n");
+		mutex_unlock(&add_mux_channel_lock);
 		return -EINVAL;
 	}
 	/* copy UL filter rules from Modem*/
@@ -539,6 +542,7 @@ int copy_ul_filter_rule_to_ipa(struct ipa_install_fltr_rule_req_msg_v01
 			ipv4_frag_eq_present = rule_req->filter_spec_list[i].
 			filter_rule.ipv4_frag_eq_present;
 	}
+	mutex_unlock(&add_mux_channel_lock);
 	return rc;
 }
 
@@ -1329,8 +1333,11 @@ static int ipa_wwan_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 				IPAWANERR("failed to config egress endpoint\n");
 
 			if (num_q6_rule != 0) {
+				/* protect num_q6_rule */
+				mutex_lock(&add_mux_channel_lock);
 				/* already got Q6 UL filter rules*/
 				rc = wwan_add_ul_flt_rule_to_ipa();
+				mutex_unlock(&add_mux_channel_lock);
 				egress_set = true;
 				if (rc)
 					IPAWANERR("install UL rules failed\n");