On Mon, 04 Nov 2019 09:49:43 +0100, Greg Kroah-Hartman wrote: > > On 11/4/19 9:32 AM, Greg Kroah-Hartman wrote: > > On 11/4/19 9:27 AM, youling 257 wrote: > > > This driver > > > https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/drivers/usb/gadget/function/f_audio_source.c > > > > > > > > > > The driver is broken and needs to be fixed. Please feel free to submit > > patches to AOSP to do so as you can trigger this easily. > > Hm, maybe the driver isn't broken... It is :) > snd_pcm_lib_preallocate_pages_for_all() is called with > SNDRV_DMA_TYPE_DEV set, so that should be fine, That's the cause. It passes NULL to the device object, which is incorrect in anyway. I guess this used to work casually just because x86 accepts the NULL device object as if an ISA device. > and the only other > buffer I can see allocate here is with a call to > snd_pcm_lib_alloc_vmalloc_buffer() which _should_ be ok, right? If the driver allocates the buffer via vmalloc (and the snd_* helper), it shouldn't do preallocate in that way. That is, the correct fix would be simply to drop snd_pcm_lib_preallocate_pages_for_all() call from the driver code. Also, a quick skimming showed that the driver needs to set snd_pcm_lib_get_vmalloc_page to the snd_pcm_ops.page ops. > I don't see any buffers coming off the stack here, unless the gadget > controller is the one creating them? That's the code before actually allocating the buffer itself. It checks the availability of mmap support on the architecture, and the helper code assumed a proper device object passed there via the preallocation helper. thanks, Takashi
