[PATCH V3] binder: ipc namespace support for android binder

[Todd Kjos]

On Fri, Nov 9, 2018 at 7:09 PM chouryzhou(周威) <chouryzhou at tencent.com> wrote:
>
> >
> > I still don't understand the dependencies on SYSVIPC or POSIX_MQUEUE.
> > It seems like this mechanism would work even if both are disabled --
> > as long as IPC_NS is enabled. Seems cleaner to change init/Kconfig and
> > allow IPC_NS if CONFIG_ANDROID_BINDER_IPC and change this line to
> > "#ifndef CONFIG_IPC_NS"
>
> Let me explain it in detail. If SYSIPC and IPC_NS are both defined,
> current->nsproxy->ipc_ns will save the ipc namespace variables. We just use
> it. If SYSIPC (or POSIX_MQUEUE) is defined while IPC_NS is not set,
> current->nsproxy->ipc_ns will always refer to init_ipc_ns in ipc/msgutil.c,
> which is also fine to us. But if neither SYSIPC nor POSIX_MQUEUE is set
> (IPC_NS can't be set in this situation), there is no current->nsproxy->ipc_ns.
> We make a fack init_ipc_ns here and use it.

Yes, I can read the code. I'm wondering specifically about SYSVIPC and
POSIX_MQUEUE. Even with your code changes, binder has no dependency on
these configs. Why are you creating one? The actual dependency with
your changes is on "current->nsproxy->ipc_ns" being initialized for
binder -- which is dependent on CONFIG_IPC_NS being enabled, isn't it?

If SYSVIPC or POSIX_MQUEUE are enabled, but IPC_NS is disabled, does this work?

>
> > why eliminate name? The string name is very useful for differentiating
> > normal "framework" binder transactions vs "hal" or "vendor"
> > transactions. If we just have a device number it will be hard to tell
> > in the logs even which namespace it belongs to. We need to keep both
> > the "name" (for which there might be multiple in each ns) and some
> > indication of which namespace this is. Maybe we assign some sort of
> > namespace ID during binder_init_ns().
>
>  I will remain the name of device. The  inum of ipc_ns can be treated as
> namespace ID in ipc_ns.
>
> > As mentioned above, we need to retain name and probably also want a ns
> > id of some sort. So context now has 3 components if IPC_NS, so maybe a
> > helper function to print context like:
> >
> > static void binder_seq_print_context(struct seq_file *m, struct
> > binder_context *context)
> > {
> > #ifdef CONFIG_IPC_NS
> >           seq_printf(m, "%d-%d-%s", context->ns_id, context->device,
> > context->name);
> > #else
> >           seq_printf(m, "%d", context->name);
> > #endif
> > }
> >
> > (same comment below everywhere context is printed)
> >
> > Should these debugfs nodes should be ns aware and only print debugging
> > info for the context of the thread accessing the node? If so, we would
> > also want to be namespace-aware when printing pids.
>
> Nowadays, debugfs is not namespace-ized, and pid namespace is not associated
> with ipc namespace.  Will it be more complicated to debug this if we just print
> the info for current thread? Because we will have to enter the ipc namespace
> firstly. But add ipc inum should be no problem.

With the name and ns id, debugging would be fine from the host-side. I
don't understand the container use cases enough to know if you need to
be able to debug binder transaction failures from within the container
-- in which case it seems like you'd want the container-version of the
PIDs -- but obviously this depends on how the containers are set up
and what the use-cases really are. I'm ok with leaving that for a
later patch.

>
> - choury -
>
>