[kamailio/kamailio] Suspected mem leak in the pua and request for ideas (Issue #3928) - sr-dev

22 Jul 2024

Hi! it seems the pua module in send_subscribe ( ) is leaking some memory because the
hentity is not released.
According to memory allocations the shmem allocated for hentity is not cleaned.
```
1454582 file = 0x70e59fd30209 "usrloc: ../../core/ut.h", func = 0x70e59fd326c8
<__func__.16> "shm_str_dup", mname = 0x70e59fd2fdf0 "usrloc",
line = 722
 698090 file = 0x604218f2fcd5 "core: core/xavp.c", func = 0x604218f31988
<__func__.9> "xavp_new_value", mname = 0x604218f2fcd0 "core",
line = 100
 360187 file = 0x70e59fd30663 "usrloc: ucontact.c", func = 0x70e59fd326b8
<__func__.17> "new_ucontact", mname = 0x70e59fd2fdf0 "usrloc",
line = 94
  34208 file = 0x70e59fc91ae9 "pua: send_subscribe.c", func = 0x70e59fc94c80
<__func__.2> "subscribe_cbparam", mname = 0x70e59fc917e0 "pua",
line = 773
   5569 file = 0x70e59fc91ae9 "pua: send_subscribe.c", func = 0x70e59fc94ca0
<__func__.1> "subs_cbparam_indlg", mname = 0x70e59fc917e0 "pua",
line = 861
     64 file = 0x70e5a231f424 "tmx: tmx_pretran.c", func = 0x70e5a2320230
<__func__.0> "tmx_check_pretran", mname = 0x70e5a231f420 "tmx",
line = 271
     64 file = 0x70e5a231f424 "tmx: tmx_pretran.c", func = 0x70e5a2320230
<__func__.0> "tmx_check_pretran", mname = 0x70e5a231f420 "tmx",
line = 250
      7 file = 0x70e59fc86854 "pua: event_list.c", func = 0x70e59fc86ad0
<__func__.1> "add_pua_event", mname = 0x70e59fc86850 "pua", line
= 72
      3 file = 0x70e5a297c249 "license: ../../core/ut.h", func = 0x70e5a297d4f8
<__func__.3> "shm_str_dup", mname = 0x70e5a297c000 "license",
line = 722
      3 file = 0x70e59fd329d4 "usrloc: udomain.c", func = 0x70e59fd35660
<__func__.22> "build_stat_name", mname = 0x70e59fd328a0
"usrloc", line = 56
```
According to mod_stats for shmem over RPC the pua module was taking double as much memory
as usrloc on the busy system.

I have tried to address the issue shown on lines 773 and 861 and added clearing of hentity
at the end of send_subscribe () :
but it had caused the subscribe_200 outside of dialog to crash kamailio because of running
the tm callback that accesses the hentity which is already free'd

So I thought perhaps another approach is required and the tm callback should clean it,
while I must say i do not 100% clear understand why this needs to be so complicated
compared to other modules. Perhaps i have missed another bug and overcomplicated things
because  the uac_r seems to be cleaned just fine.
The issue around the hentity does not seem to be solved in the latest releases while this
is 5.3-something custom build.

Anyway my last resort that could help is convert to use tm to clear memory once it is
done, in tm/uac.c : t_uac_prepare() is registering a callback with release function
```
	if(uac_r->cb && insert_tmcb(&(new_cell->tmcb_hl), uac_r->cb_flags,
								*(uac_r->cb), uac_r->cbp, NULL)!=1){
		ret=E_OUT_OF_MEM;
		LM_ERR("short of tmcb shmem\n");
		goto error1;
	}
int insert_tmcb(struct tmcb_head_list *cb_list, int types,
				transaction_cb f, void *param,
				release_tmcb_param rel_func)
{
```
is there any example of using such a relfunc in the other modules? Or anyone else has see
the pua causing a mem leak when it is subscribed to reginfo from the config? I would
appreciate some ideas what could be the issue and the solution.

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