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Subject: Re: [alsa-devel] [PATCH] ASoC: soc-core: Fix null pointer dereference
 in soc_find_component
From:   Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To:     Rohit kumar <rohitkr@codeaurora.org>, plai@codeaurora.org,
        bgoswami@codeaurora.org, asishb@codeaurora.org,
        lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz,
        tiwai@suse.com, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org, rohkumar@qti.qualcomm.com,
        srinivas.kandagatla@linaro.org, vinod.koul@linaro.org
Cc:     Ajit Pandey <ajitp@codeaurora.org>,
        Liam Girdwood <liam.r.girdwood@linux.intel.com>
References: <1547194442-1487-1-git-send-email-rohitkr@codeaurora.org>
 <d8726e9a-3477-a573-8c1a-dd8245068802@linux.intel.com>
Message-ID: <4886ed21-65d2-159d-afcd-bb26dcde636e@linux.intel.com>
Date:   Fri, 11 Jan 2019 15:49:08 -0600
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> Thanks for the overnight fix. This update fixes the issue on my 
> Skylake XPS13 test device (blind testing since I don't understand what 
> the code does).
>
> Tested-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

I need to take this back, this set of changes (initial+fix) causes an 
error with our HDMI support

[   17.437684] sof-audio sof-audio: created machine bxt-pcm512x
[   17.585279] bxt-pcm512x bxt-pcm512x: ASoC: failed to init link iDisp1
[   17.585639] bxt-pcm512x bxt-pcm512x: snd_soc_register_card failed -517

Removing your changes restores the functionality

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?

[1] 
https://elixir.bootlin.com/linux/latest/source/sound/soc/intel/boards/bxt_da7219_max98357a.c#L475

[   18.205812] plb: platform name sof-audio
[   18.206059] plb: cpu_name (null)
[   18.206234] plb: platform name 0000:00:0e.0
[   18.206459] plb: returning -EPROBE_DEFER 1
[   18.206686] bxt-pcm512x bxt-pcm512x: ASoC: failed to init link iDisp1
[   18.207054] bxt-pcm512x bxt-pcm512x: snd_soc_register_card failed -517

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index cbafbdd02483..ae731212f82b 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -1133,11 +1133,15 @@ static int soc_init_dai_link(struct snd_soc_card 
*card,
          * Defer card registration if platform dai component is not 
added to
          * component list.
          */
+       pr_err("plb: platform name %s\n", link->platform->name);
         if (link->platform->of_node || link->platform->name)
                 if (!soc_find_component(link->platform->of_node,
link->platform->name))
-                       return -EPROBE_DEFER;
+                 {
+                         pr_err("plb: returning -EPROBE_DEFER 1\n");
+                         return -EPROBE_DEFER;

+                 }
         /*
          * CPU device may be specified by either name or OF node, but
          * can be left unspecified, and will be matched based on DAI
@@ -1154,9 +1158,14 @@ static int soc_init_dai_link(struct snd_soc_card 
*card,
          * Defer card registration if cpu dai component is not added to
          * component list.
          */
+       pr_err("plb: cpu_name %s\n", link->cpu_name);
         if (link->cpu_of_node || link->cpu_name)
                 if (!soc_find_component(link->cpu_of_node, link->cpu_name))
-                       return -EPROBE_DEFER;
+                 {
+                         pr_err("plb: returning -EPROBE_DEFER 2\n");
+                         return -EPROBE_DEFER;
+
+                 }

         /*
          * At least one of CPU DAI name or CPU device name/node must be