gsm48_parse_meas_rep(): set num_cell=0 if no neighbor cells are reported

Set mr->num_cell to 0 if the bits reflect 0x7, which means that no neighbor
cell measurements are enclosed in the report.

The code in gsm48_parse_meas_rep() acknowledges that, but nevertheless left
num_cell == 7, and evaluating code commonly runs into the mistake of assuming
that actually seven neighbors are being reported on, like:

 MEASUREMENT REPORT
   0: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
   1: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
   2: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
   3: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
   4: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
   5: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
   6: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0

There are only up to 6 slots for neighbors, the above listing actually printed
7, because num_cell == 7, which is a potential segfault.  (sometimes it printed
uninitialized values instead of 0)

We could fix all meas rep consumers to know what num_cell == 7 means, but
instead setting it to 0 trivially fixes all of them.

Change-Id: If2da33915e9a5eba02e83fa5372908ab10044911

0 files changed, 0 insertions, 0 deletions