Crash in lte-softmodem upon receipt of RRCConnectionReestablishmentRequest

Report in mailing list: https://lists.eurecom.fr/sympa/arc/openair5g-user/2020-07/msg00033.html

Relevant part:

When I move my UE from the master eNB to the slave eNB the following happens:
- the slave initiates a HandoverRequest and sends it to the master
- the master acknowledges the HandoverRequest
- the slave tries to connect to the UE and prints the following message
"LTE_RRCConnectionReestablishmentRequest without UE context, let's reject the UE"
cancel the HO and crashes.

The crash was reproducible in other environment with Samsung A3 phone, even without Handover initiation over X2AP. UE was quickly moved from one eNB area to another eNB area.

The reason is that UE sends RRCConnectionReestablishmentRequest to eNB that has no UE context for it, and lte-softmodem dereferences a NULL pointer. Excerpt from communication is attached.RRCConnectionReestablishment_crash.pcapng

Cell ID is 0xe100, PCI 1. RRCConnectionReestablishment identifies UE as connected to PCI 0.

Reproducible on develop branch commit bdc1fa4e, master branch 7cc5a63a and may be later as well.