ASoC: soc-compress: prevent the potentially use of null pointer

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ASoC: soc-compress: prevent the potentially use of null pointer There is one call trace that snd_soc_register_card() ->snd_soc_bind_card()->soc_init_pcm_runtime() ->snd_soc_dai_compress_new()->snd_soc_new_compress(). In the trace the 'codec_dai' transfers from card->dai_link, and we can see from the snd_soc_add_pcm_runtime() in snd_soc_bind_card() that, if value of card->dai_link->num_codecs is 0, then 'codec_dai' could be null pointer caused by index out of bound in 'asoc_rtd_to_codec(rtd, 0)'. And snd_soc_register_card() is called by various platforms. Therefore, it is better to add the check in the case of misusing. And because 'cpu_dai' has already checked in soc_init_pcm_runtime(), there is no need to check again. Adding the check as follow, then if 'codec_dai' is null, snd_soc_new_compress() will not pass through the check 'if (playback + capture != 1)', avoiding the leftover use of 'codec_dai'.

References

• https://git.kernel.org/stable/c/68a69ad8df959e5211ed4a8e120783b2d352ea74
• https://git.kernel.org/stable/c/4639c1d97f385f4784f44d66a3da0672f4951ada
• https://git.kernel.org/stable/c/fc237b8d624f4bcb0f21a532627ce4e3b3a85569
• https://git.kernel.org/stable/c/08af6da684b44097ea09f1d74d5858b837ed203b
• https://git.kernel.org/stable/c/f69a75cb8a98c6c487d620442c68595726a69f60
• https://git.kernel.org/stable/c/de2c6f98817fa5decb9b7d3b3a8a3ab864c10588