[LEDE-DEV] [PATCH] libubus: initialize list member for ubus_auto_conn's timer

[Felix Fietkau]

On 2016-12-13 08:41, Alexandru Ardelean wrote:
> Every once in a while, we'll get stacktrace:
> ```
> (gdb) bt
> \#0  0xb7bc4668 in _list_del (entry=0x10015688 <conn+116>) at /home/sandu/work/Wrt/openwrt/build_dir/target-powerpc_8540_uClibc-0.9.33.2_ewok/libubox-2015-06-29/list.h:83
> \#1  list_del (entry=0x10015688 <conn+116>) at /home/sandu/work/Wrt/openwrt/build_dir/target-powerpc_8540_uClibc-0.9.33.2_ewok/libubox-2015-06-29/list.h:90
> \#2  uloop_timeout_cancel (timeout=timeout at entry=0x10015688 <conn+116>) at /home/sandu/work/Wrt/openwrt/build_dir/target-powerpc_8540_uClibc-0.9.33.2_ewok/libubox-2015-06-29/uloop.c:474
> \#3  0x10003794 in ubus_auto_shutdown (conn=0x10015614 <conn>) at /home/sandu/work/Wrt/openwrt/staging_dir/target-powerpc_8540_uClibc-0.9.33.2_ewok/usr/include/libubus.h:249
> \#4  module_ubus_fini () at ubus.c:64
> \#5  0x100013fc in main (argc=<optimized out>, argv=<optimized out>) at module.c:128
> ```
> 
> In our code, `ubus_auto_connect()` is called, then due to some logic,
> the module has to quickly stop, calling ubus_auto_shutdown().
> 
> It seems that there is case in where the `timer` timeout, is not yet
> registered with the internal list of timeouts from uloop, which
> ends up trying to delete an invalid list.
> 
> So, one solution is to init the list element of the `timer` of
> the `ubus_auto_conn` struct.
> 
> Signed-off-by: Alexandru Ardelean <ardeleanalex at gmail.com>
I think this patch is a workaround that simply hides the real issue.
uloop_timeout_cancel will only call list_del if the timer 'pending' flag
is set.

It seems to me that you might be using ubus_auto_connect on
uninitialized memory. If that's the case, you might run into issues in
other places as well, and you should just add a memset to your application.

- Felix