The idea of ts_alloc()/ts_free() dates back to the very early days of
OpenBSC, where we didn't yet have a fixed PCHAN type assigned for every
lchan in a BTS. However, ever since, PCHAN types (channel combinations)
are configured by OML in a certain way, and we only allocate LCHANs
inside PCHANs of a matching type. There should be no PCHANs with
type GSM_PCHAN_NONE, unless those that you don't want to use for
administraive reasons or the like.
show net with an CCCH+SDCCH/4+CBCH channel active caused bts_chan_load to read
from invalid memory. Fix this by making sure the pchan array is large enough.
==30346==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fff9bdc5dc8 at pc 0x5aeece bp 0x7fff9bdc5350 sp 0x7fff9bdc5348
READ of size 4 at 0x7fff9bdc5dc8 thread T0
#0 0x5aeecd in bts_chan_load /home/alphaone/scm/osmo/openbsc/openbsc/src/libbsc/chan_alloc.c:490
#1 0x5af706 in network_chan_load /home/alphaone/scm/osmo/openbsc/openbsc/src/libbsc/chan_alloc.c:511
#2 0x4b7410 in net_dump_vty /home/alphaone/scm/osmo/openbsc/openbsc/src/libbsc/bsc_vty.c:208
#3 0x4b5f23 in show_net /home/alphaone/scm/osmo/openbsc/openbsc/src/libbsc/bsc_vty.c:227
#4 0x7fdabaa425bd in cmd_execute_command_real /home/alphaone/scm/osmo/libosmocore/src/vty/command.c:2042
#5 0x7fdabaa3f124 in cmd_execute_command /home/alphaone/scm/osmo/libosmocore/src/vty/command.c:2077
#6 0x7fdabaa850e9 in vty_command /home/alphaone/scm/osmo/libosmocore/src/vty/vty.c:402
#7 0x7fdabaa75962 in vty_execute /home/alphaone/scm/osmo/libosmocore/src/vty/vty.c:666
#8 0x7fdabaa6d947 in vty_read /home/alphaone/scm/osmo/libosmocore/src/vty/vty.c:1408
#9 0x7fdabaa9165f in client_data /home/alphaone/scm/osmo/libosmocore/src/vty/telnet_interface.c:119
#10 0x7fdaba7860b6 in osmo_select_main /home/alphaone/scm/osmo/libosmocore/src/select.c:160
#11 0x43c656 in main /home/alphaone/scm/osmo/openbsc/openbsc/src/osmo-nitb/bsc_hack.c:355
#12 0x7fdab92604bc (/lib64/libc.so.6+0x224bc)
#13 0x43b6cc (/home/alphaone/local/osmo-asan/bin/osmo-nitb+0x43b6cc)
Address 0x7fff9bdc5dc8 is located in stack of thread T0 at offset 232 in frame
#0 0x4b5faf in net_dump_vty /home/alphaone/scm/osmo/openbsc/openbsc/src/libbsc/bsc_vty.c:182
This frame has 3 object(s):
[32, 40) ''
[96, 104) ''
[160, 224) 'pl'
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow /home/alphaone/scm/osmo/openbsc/openbsc/src/libbsc/chan_alloc.c:490 bts_chan_load
The reason for this is quite simple: We want to make sure anyone
running a customized version of OpenBSC to operate a network will
have to release all custom modifiations to the source code.
When the cell becomes visible we will be bombed with location
updating requests and to reduce the load on the network we should
assign as many channels for it as possible. During load peek it
is even more important than to have a spare voice channel and in
general the LU procedure is pretty fast.
A channel will be released in case of
* Errors via the clear_request callback...
* no more transactions and operations are going on.
This means that if we do something without a transaction
the channel might be closed down right away. The bug fix
will be to create a transaction/operation.
With handover and late/early assignment there might be two channels
for one subscriber and only the BSC knows which one to use, so use
the gsm_subscriber_connection everywhere...
Free all allocated channels on the TRX that failed, go through
lchan_free to signal higher layers and then force a reset of
the channel. Make the TRX and TS unusable by setting the operational
set to 0 (not really defined) which should be reset once the
RSL is coming up again.
Harald Welte
Daniel Willmann