On Fri, Mar 31, 2023 at 10:14:11AM +0300, Péter Ujfalusi wrote:
> Hi Dan,
>
> On 31/03/2023 09:58, Dan Carpenter wrote:
> > Hello Guennadi Liakhovetski,
> >
> > This is a semi-automatic email about new static checker warnings.
> >
> > The patch e3720f92e023: "ASoC: SOF: avoid a NULL dereference with
> > unsupported widgets" from Mar 29, 2023, leads to the following Smatch
> > complaint:
> >
> > sound/soc/sof/ipc4-topology.c:2353 sof_ipc4_route_setup()
> > error: we previously assumed 'sink_fw_module' could be null (see line 2351)
> >
> > sound/soc/sof/ipc4-topology.c:2353 sof_ipc4_route_setup()
> > error: we previously assumed 'src_fw_module' could be null (see line 2351)
> >
> > sound/soc/sof/ipc4-topology.c
> > 2350
> > 2351 if (!src_fw_module || !sink_fw_module) {
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > One of these is NULL.
> >
> > 2352 /* The NULL module will print as "(efault)" */
> > 2353 dev_err(sdev->dev, "source %s or sink %s widget weren't set up properly\n",
> > 2354 src_fw_module->man4_module_entry.name,
> > 2355 sink_fw_module->man4_module_entry.name);
> > ^^^^^^^^^^^^^^
> > Both are dereferenced. The comment is very puzzling.
>
> if src_fw_module is NULL then the print will be:
> source (efault) or sink sink.module.name widget weren't set up properly
>
> Guennadi is relying on some black magic in the printk system to handle
> the printing instead of open coding.
I've done compiler related work and explored some weird aspect of the
C language and I am so fascinated by this. I would have thought it
crashes before the function is called. I cannot even imagine how black
magic like this would work.
Is there anyway I can test this?
regards,
dan carpenter
