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

Overview

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.

Affected

• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < 3fa521c3c54b42e16cad8ade76551113a783752b
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < 3f06f3f5b16212f180764654a9398ff5f7a855c8
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < f1c05c41d07b874635d681ae328d13ec550470c5
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < 5a625fc2284e35f33693efd9534aebaca3b005d4
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < 6d3e202670b819c414076a5d07dffac8a39274ad
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < 6c94877b6bab9185898bcad4b082ff5592558921
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < d1f643b1c0258bd519146f7a342bbb394d413912
• Linux >= 88a8516a2128a6d078a106ead48092240e8a138f < 1739a976312e110c93a8dee66a1cdf893a1b187e
• Linux 2.6.39

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.