The code like:
typedef struct {
  struct umdb_list_head_st *list_head;
  struct umdb_list_node_st *current;
} umdb_util_it_t;
typedef umdb_util_it_t umdb_dbms_hl_oper_list_iterator_t;

umdb_dbms_hl_oper_list_iterator_t 
umdb_dbms_oper_list_find_element (umdb_dbms_hl_oper_list_handle_t *list, 
                                  MSF_UINT8 src_mod_id,
                                  MSF_UINT16 transaction_id)
{
  umdb_dbms_hl_oper_list_iterator_t it;
  umdb_dbms_oper_list_elem_t *elem;

  it = umdb_dbms_oper_list_get_iterator (list);

  while (!umdb_dbms_oper_list_equals_end (&it)) {
    elem = (umdb_dbms_oper_list_elem_t*)it.current;

    if (elem->ml_transaction_id == transaction_id &&
        elem->src_mod_id == src_mod_id) {
      break;
    }

    umdb_dbms_oper_list_iterator_next (&it);
  }

  return it;
}

The asm code like:
00000000 <umdb_dbms_oper_list_find_element>:
   0:	b5f0      	push	{r4, r5, r6, r7, lr}
   2:	b087      	sub	sp, #28
   4:	ac02      	add	r4, sp, #8
   6:	1c05      	adds	r5, r0, #0
   8:	ae04      	add	r6, sp, #16
   a:	1c20      	adds	r0, r4, #0
   c:	1c17      	adds	r7, r2, #0
   e:	9301      	str	r3, [sp, #4]
  10:	f7ff fffe 	bl	0 <umdb_dbms_oper_list_find_element>
  14:	cc03      	ldmia	r4!, {r0, r1}
  16:	c603      	stmia	r6!, {r0, r1}
  18:	e00a      	b.n	30 <umdb_dbms_oper_list_find_element+0x30>
  1a:	6863      	ldr	r3, [r4, #4]
  1c:	9801      	ldr	r0, [sp, #4]
  1e:	8a1a      	ldrh	r2, [r3, #16]
  20:	4282      	cmp	r2, r0
  22:	d102      	bne.n	2a <umdb_dbms_oper_list_find_element+0x2a>
  24:	7a1b      	ldrb	r3, [r3, #8]
  26:	42bb      	cmp	r3, r7
  28:	d008      	beq.n	3c <umdb_dbms_oper_list_find_element+0x3c>
  2a:	a804      	add	r0, sp, #16
  2c:	f7ff fffe 	bl	0 <umdb_dbms_oper_list_find_element>
  30:	ac04      	add	r4, sp, #16
  32:	1c20      	adds	r0, r4, #0
  34:	f7ff fffe 	bl	0 <umdb_dbms_oper_list_find_element>
  38:	2800      	cmp	r0, #0
  3a:	d0ee      	beq.n	1a <umdb_dbms_oper_list_find_element+0x1a>
  3c:	1c2a      	adds	r2, r5, #0
  3e:	ab04      	add	r3, sp, #16
  40:	b007      	add	sp, #28
  42:	cb03      	ldmia	r3!, {r0, r1}
  44:	c203      	stmia	r2!, {r0, r1}
  46:	1c28      	adds	r0, r5, #0
  48:	bdf0      	pop	{r4, r5, r6, r7, pc}
  4a:	46c0      	nop			; (mov r8, r8)

It show the return struct is not safe here, it still use the stack after sp+0x28.
  40:	b007      	add	sp, #28
  42:	cb03      	ldmia	r3!, {r0, r1}
  44:	c203      	stmia	r2!, {r0, r1}