From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> From: Takashi Iwai <tiwai@xxxxxxx> commit 21cba9c5359dd9d1bffe355336cfec0b66d1ee52 upstream. Some USB audio firmware seem to report broken dB values for the volume controls, and this screws up applications like PulseAudio who blindly trusts the given data. For example, Edifier G2000 reports a PCM volume from -128dB to -127dB, and this results in barely inaudible sound. This patch adds a sort of sanity check at parsing the dB values in USB-audio driver and disables the dB reporting if the range looks bogus. Here, we assume -96dB as the bottom line of the max dB. Note that, if one can figure out that proper dB range later, it can be patched in the mixer maps. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=211929 Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210227105737.3656-1-tiwai@xxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/usb/mixer.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -1301,6 +1301,17 @@ no_res_check: /* totally crap, return an error */ return -EINVAL; } + } else { + /* if the max volume is too low, it's likely a bogus range; + * here we use -96dB as the threshold + */ + if (cval->dBmax <= -9600) { + usb_audio_info(cval->head.mixer->chip, + "%d:%d: bogus dB values (%d/%d), disabling dB reporting\n", + cval->head.id, mixer_ctrl_intf(cval->head.mixer), + cval->dBmin, cval->dBmax); + cval->dBmin = cval->dBmax = 0; + } } return 0;
