sgsn: Reject PdpActReq if no GTP pdp ctx exists
It could happen that SGSN drops GTP side of a pdp ctx (pdp->lib=NULL)
while still maintaing the other side (to notify about the entire pdp ctx
being torn down). If a PdpActReq arrives during that time, we need to
account for that situation, otherwise osmo-sgsn crashes accessing
pdp->lib.
If no pdp->lib is found at that time, let's reject the request and
expect at some point later in time the entire pdp context will be
destroyed and reestablished.
Related: OS#4173
Change-Id: I6dd87557ebb26fdbd280504abde10d976acecf64
diff --git a/src/sgsn/gprs_sm.c b/src/sgsn/gprs_sm.c
index 8cf5c5d..f8019ab 100644
--- a/src/sgsn/gprs_sm.c
+++ b/src/sgsn/gprs_sm.c
@@ -491,6 +491,11 @@
/* Check if NSAPI is already in use */
pdp = sgsn_pdp_ctx_by_nsapi(mmctx, act_req->req_nsapi);
if (pdp) {
+ /* Make sure pdp ctx was not already torn down on GTP side */
+ if (!pdp->lib) {
+ gsm_cause = GSM_CAUSE_REACT_RQD;
+ goto no_context;
+ }
/* We already have a PDP context for this TLLI + NSAPI tuple */
if (pdp->sapi == act_req->req_llc_sapi &&
pdp->ti == transaction_id) {