| From | Sasha Levin <> | Subject | [PATCH 5.2 019/135] ALSA: usb-audio: Fix an OOB bug in parse_audio_mixer_unit | Date | Thu, 22 Aug 2019 13:06:15 -0400 |
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From: Hui Peng <benquike@gmail.com>
commit daac07156b330b18eb5071aec4b3ddca1c377f2c upstream.
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
``` struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; } ```
This patch fixes the bug by add a sanity check on the length of the descriptor.
Reported-by: Hui Peng <benquike@gmail.com> Reported-by: Mathias Payer <mathias.payer@nebelwelt.net> Cc: <stable@vger.kernel.org> Signed-off-by: Hui Peng <benquike@gmail.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- sound/usb/mixer.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 2051a64fa2904..b5927c3d5bc0b 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -745,6 +745,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL; + if (desc->bLength < sizeof(*desc) + desc->bNrInPins) + return -EINVAL; switch (state->mixer->protocol) { case UAC_VERSION_1: -- 2.20.1
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