[sr-dev] [kamailio/kamailio] Segmentation fault in rpc_mod_print function while shutting down server. (#2433)

Mon Aug 10 11:42:09 CEST 2020

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### Description

We have segfault in Kamailio v5.3.1 installed on Debain 9.x 64 bit occured while kamailio was shutting down while our script tryed to get metric using kamcmd utility at the same time.

### Troubleshooting

No troubleshooting was done, since it happened on a production server. We simply restarted the server.

#### Reproduction

The problem periodically happens on production servers during restart. Kamailio crashes when one of our scripts tried getting statistics about websocket and tls modules using kamcmd during server restart. As I see in core dump, shared memory was already freed when rpc_mod_print called in the child process.

#### Debugging Data

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```
core.kamailio.17684

/var/lib/ums/sbin/kamailio

GNU gdb (Debian 7.12-6) 7.12.0.20161007-git
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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and "show warranty" for details.
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For bug reporting instructions, please see:
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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /var/lib/ums/sbin/kamailio...done.
[New LWP 17684]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/var/lib/ums/sbin/kamailio -m 2048 -M 12 -P /var/run/kamailio/kamailio.pid -f /'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  __strcmp_ssse3 () at ../sysdeps/x86_64/multiarch/../strcmp.S:1197
#0  __strcmp_ssse3 () at ../sysdeps/x86_64/multiarch/../strcmp.S:1197
#1  0x00007ff4d6ddb2f5 in rpc_mod_print (rpc=0x7ff4d66f0540 <binrpc_callbacks>, ctx=0x7fff11cd5658, mname=0x1f140b8 "tls", stats=0x1f2f180, flag=2) at mod_stats.c:117
#2  0x00007ff4d6ddb0eb in rpc_mod_print_one (rpc=0x7ff4d66f0540 <binrpc_callbacks>, ctx=0x7fff11cd5658, mname=0x1f140b8 "tls", pkg_stats=0x1f2d9c0, shm_stats=0x1f2f180, flag=2) at mod_stats.c:159
#3  0x00007ff4d6ddaee1 in rpc_mod_mem_stats_mode (rpc=0x7ff4d66f0540 <binrpc_callbacks>, ctx=0x7fff11cd5658, fmode=0) at mod_stats.c:239
#4  0x00007ff4d6dda84f in rpc_mod_mem_stats (rpc=0x7ff4d66f0540 <binrpc_callbacks>, ctx=0x7fff11cd5658) at mod_stats.c:251
#5  0x00007ff4d64bfc80 in process_rpc_req (buf=0x1f140a4 "\241\003\026t\256\214=\221\nmod.stats", size=29, bytes_needed=0x7fff11cd5aa0, sh=0x7fff11cd5a10, saved_state=0x1f240a8) at binrpc_run.c:678
#6  0x00007ff4d64ad72f in handle_stream_read (s_c=0x1f14070, idx=-1) at io_listener.c:511
#7  0x00007ff4d64a9121 in handle_io (fm=0x7ff55a4e4ae0, events=1, idx=-1) at io_listener.c:706
#8  0x00007ff4d64a793a in io_wait_loop_epoll (h=0x7ff4d66f0348 <io_h>, t=10, repeat=0) at ./../../core/io_wait.h:1062
#9  0x00007ff4d649b62c in io_listen_loop (fd_no=2, cs_lst=0x1e28940) at io_listener.c:281
#10 0x00007ff4d64d172c in mod_child (rank=0) at ctl.c:338
#11 0x0000000000638c14 in init_mod_child (m=0x7ff55a3634b0, rank=0) at core/sr_module.c:780
#12 0x000000000063862d in init_mod_child (m=0x7ff55a363b78, rank=0) at core/sr_module.c:776
#13 0x000000000063862d in init_mod_child (m=0x7ff55a364018, rank=0) at core/sr_module.c:776
#14 0x000000000063862d in init_mod_child (m=0x7ff55a364528, rank=0) at core/sr_module.c:776
#15 0x000000000063862d in init_mod_child (m=0x7ff55a3649c8, rank=0) at core/sr_module.c:776
#16 0x000000000063862d in init_mod_child (m=0x7ff55a365140, rank=0) at core/sr_module.c:776
#17 0x000000000063862d in init_mod_child (m=0x7ff55a3657b0, rank=0) at core/sr_module.c:776
#18 0x000000000063862d in init_mod_child (m=0x7ff55a365c38, rank=0) at core/sr_module.c:776
#19 0x00000000006385b2 in init_child (rank=0) at core/sr_module.c:825
#20 0x000000000043140c in main_loop () at main.c:1753
#21 0x000000000043df6f in main (argc=9, argv=0x7fff11cd9dd8) at main.c:2802
```

#### Log Messages

No any useful logs available.

#### SIP Traffic

No SIP traffic available.

### Possible Solutions

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### Additional Information

  * **Kamailio Version** - output of `kamailio -v`

```
version: kamailio 5.3.1 (x86_64/linux) 283e46
flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES
ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB
poll method support: poll, epoll_lt, epoll_et, sigio_rt, select.
id: 283e46
compiled on 14:23:37 Jul 28 2020 with clang 9.0

```

* **Operating System**:

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Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...;
Kernel details (output of `uname -a`)
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```
Linux devhpbx005-1.vx 4.9.0-12-amd64 #1 SMP Debian 4.9.210-1 (2020-01-20) x86_64 GNU/Linux
```

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