ALSA: usb-audio: Complete cleanup after system-resume errors

Summary

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Complete cleanup after system-resume errors A failed system resume can leave the card unusable until reboot. usb_audio_resume() jumps to err_out when snd_usb_pcm_resume() or snd_usb_mixer_resume() fails. The error path skips the out: block, which restores D0 and decrements chip->num_suspended_intf. The card stays in SNDRV_CTL_POWER_D3hot, so later control access blocks in snd_power_ref_and_wait(). USB core logs an interface resume callback error. It does not retry that callback, so a later callback cannot complete the skipped cleanup. usb_audio_suspend() increments num_suspended_intf before returning success. A system-resume callback must consume the system-suspend count even if a component resume fails. Otherwise, the stranded count skews later suspend and resume cycles. Do not apply this cleanup to runtime-resume errors. Runtime PM can retry -EAGAIN or -EBUSY without another suspend callback. The count must continue to describe that suspended interface. Other runtime-resume errors latch runtime_error in the PM core and do not cause an immediate callback retry. Both parts of the system-resume error path are longstanding. Commit 88a8516a2128a ("ALSA: usbaudio: implement USB autosuspend") introduced err_out past the D0 restore. Commit 862b2509d157c ("ALSA: usb-audio: Fix inconsistent card PM state after resume") later moved num_suspended_intf-- into the out: block. The error path now skips both operations. No third-party code is needed to reach the error path. snd_usb_mixer_resume() ends in snd_usb_mixer_activate(), which returns the result of usb_submit_urb() for devices that have a mixer status URB. Its mixer->private_resume hook can also fail through scarlett2_init_notify(). snd_usb_pcm_resume() issues a SET_CUR request to a UAC3 power domain. It can return -EPIPE or -EIO when the device stalls the request. Route a component error through out: only when system_suspend is nonzero. Continue to return runtime-resume errors through err_out. Later component resume stages remain skipped. The original error still reaches USB core. A later transfer can fail if the device did not recover. I reproduced the system-resume failure on an Audient iD14 MkI with an out-of-tree diagnostic mixer resume hook. An injected -EIO on the unpatched core left control readers in uninterruptible sleep in snd_power_ref_and_wait() until a reboot. With this patch, the same failure restored control access. A second system suspend and resume also succeeded after I disabled fault injection.