Re: [alsa-devel] [PATCH] ASoC: soc-core: Fix null pointer dereference in soc_find_component

[Matthias Reichl]

On Tue, Jan 15, 2019 at 01:35:07PM -0600, Pierre-Louis Bossart wrote:
> 
> On 1/14/19 6:06 PM, Mark Brown wrote:
> > On Fri, Jan 11, 2019 at 03:49:08PM -0600, Pierre-Louis Bossart wrote:
> > 
> > > Adding some traces I can see that the the platform name we use doesn't seem
> > > compatible with your logic. All the Intel boards used a constant platform
> > > name matching the PCI ID, see e.g. [1], which IIRC is used to bind
> > > components. Liam, do you recall in more details if this is really required?
> > That's telling me that either snd_soc_find_components() isn't finding
> > components in the same way that we do when we bind things which isn't
> > good or we're binding links without having fully matched everything on
> > the link which also isn't good.
> > 
> > Without a system that shows the issue I can't 100% confirm but I think
> > it's the former - I'm fairly sure that those machines are relying on the
> > component name being initialized to fmt_single_name() in
> > snd_soc_component_initialize().  That is supposed to wind up using
> > dev_name() (which would be the PCI address for a PCI device) as the
> > basis of the name.  What I can't currently see is how exactly that gets
> > bound (or how any of the other links avoid trouble for that matter).  We
> > could revert and push this into cards but I would rather be confident
> > that we understand what's going on, I'm not comfortable that we aren't
> > just pushing the breakage around rather than fixing it.  Can someone
> > with an x86 system take a look and confirm exactly what's going on with
> > binding these cards please?
> 
> Beyond the fact that the platform_name seems to be totally useless,
> additional tests show that the patch ('ASoC: soc-core: defer card probe
> until all component is added to list') adds a new restriction which
> contradicts existing error checks.
> 
> None of the Intel machine drivers set the dailink "cpu_name" field but use
> the "cpu_dai_name" field instead. This was perfectly legit as documented by
> the code at the end of soc_init_dai_link()

This should be fixed by the patch
"ASoC: core: Don't defer probe on optional, NULL components" which Mark
already applied to his tree. See
http://mailman.alsa-project.org/pipermail/alsa-devel/2019-January/144323.html

Maybe the defer card probe logic needs to be extended to also check if
dai_link_name had already been registered (either cpu or cpu_dai_name
needs to be set), not 100% sure which problem the defer card probe patch
was trying to solve.

so long,

Hias

> 
>     /*
>      * At least one of CPU DAI name or CPU device name/node must be
>      * specified
>      */
>     if (!link->cpu_dai_name &&
>         !(link->cpu_name || link->cpu_of_node)) {
>         dev_err(card->dev,
>             "ASoC: Neither cpu_dai_name nor cpu_name/of_node are set for
> %s\n",
>             link->name);
>         return -EINVAL;
>     }
> 
> The code contributed by Qualcomm only checks for cpu_name, which prevents
> the init from completing.
> 
> So if we want to be consistent, the new code should be something like:
> 
> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> index b680c673c553..2791da9417f8 100644
> --- a/sound/soc/soc-core.c
> +++ b/sound/soc/soc-core.c
> @@ -1154,7 +1154,7 @@ static int soc_init_dai_link(struct snd_soc_card
> *card,
>          * Defer card registartion if cpu dai component is not added to
>          * component list.
>          */
> -       if (!soc_find_component(link->cpu_of_node, link->cpu_name))
> +       if (!link->cpu_dai_name && !soc_find_component(link->cpu_of_node,
> link->cpu_name))
>                 return -EPROBE_DEFER;
> 
>         /*
> 
> or try to call soc_find_component with both cpu_name or cpu_dai_name, if
> this makes sense?
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