osmo-bts-{trx,virtual}: check lchan against NULL in bts_model_l1sap_down()

Even though it's unlikely, get_lchan_by_chan_nr() *may* return NULL.

Change-Id: I1a815c9675eebc16640b62308499dd784fc206bd
Related: OS#1572
---
M src/osmo-bts-trx/l1_if.c
M src/osmo-bts-virtual/l1_if.c
2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/src/osmo-bts-trx/l1_if.c b/src/osmo-bts-trx/l1_if.c
index 6e290ee..7652117 100644
--- a/src/osmo-bts-trx/l1_if.c
+++ b/src/osmo-bts-trx/l1_if.c
@@ -401,6 +401,13 @@
 		else /* u.act_req used by PRIM_INFO_{ACTIVATE,DEACTIVATE,MODIFY} */
 			chan_nr = l1sap->u.info.u.act_req.chan_nr;
 		lchan = get_lchan_by_chan_nr(trx, chan_nr);
+		if (OSMO_UNLIKELY(lchan == NULL)) {
+			LOGP(DL1C, LOGL_ERROR,
+			     "Rx MPH-INFO.req (type=0x%02x) for non-existent lchan (%s)\n",
+			     l1sap->u.info.type, rsl_chan_nr_str(chan_nr));
+			rc = -ENODEV;
+			break;
+		}
 
 		switch (l1sap->u.info.type) {
 		case PRIM_INFO_ACT_CIPH:
diff --git a/src/osmo-bts-virtual/l1_if.c b/src/osmo-bts-virtual/l1_if.c
index e0536d3..235c399 100644
--- a/src/osmo-bts-virtual/l1_if.c
+++ b/src/osmo-bts-virtual/l1_if.c
@@ -356,6 +356,13 @@
 		else /* u.act_req used by PRIM_INFO_{ACTIVATE,DEACTIVATE,MODIFY} */
 			chan_nr = l1sap->u.info.u.act_req.chan_nr;
 		lchan = get_lchan_by_chan_nr(trx, chan_nr);
+		if (OSMO_UNLIKELY(lchan == NULL)) {
+			LOGP(DL1C, LOGL_ERROR,
+			     "Rx MPH-INFO.req (type=0x%02x) for non-existent lchan (%s)\n",
+			     l1sap->u.info.type, rsl_chan_nr_str(chan_nr));
+			rc = -ENODEV;
+			break;
+		}
 
 		switch (l1sap->u.info.type) {
 		case PRIM_INFO_ACT_CIPH:

