In function msm_pcm_playback_close() in all Android releases from CAF using the Linux kernel prtd is assigned substream->runtime->private_data. Later prtd is freed. However prtd is not sanitized and set to NULL resulting in a dangling pointer. There are other functions that access the same memory (substream->runtime->private_data) with a NULL check such as msm_pcm_volume_ctl_put() which means this freed memory could be used.

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Android ALSA PCM Playback Kernel Module Memory Misreference Vulnerability

Android is a Linux-based open source operating system jointly developed by Google and the Open Handset Alliance OHA, of which the ALSA PCM Playback Kernel Module is an audio playback kernel module. A security vulnerability exists in the 'msmpcmplaybackclose' function of the ALSA PCM Playback Kern...