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[128.210.107.27]) by smtp.googlemail.com with ESMTPSA id y19sm14805008ioj.62.2019.08.13.19.37.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Aug 2019 19:37:06 -0700 (PDT) From: Hui Peng To: security@kernel.org Cc: Hui Peng , Mathias Payer , Jaroslav Kysela , Takashi Iwai , Thomas Gleixner , Allison Randal , YueHaibing , Wenwen Wang , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: [PATCH] Fix an OOB bug in parse_audio_mixer_unit Date: Tue, 13 Aug 2019 22:36:24 -0400 Message-Id: <20190814023625.21683-1-benquike@gmail.com> X-Mailer: git-send-email 2.22.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Hui Peng Reported-by: Hui Peng Reported-by: Mathias Payer --- sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err; + int desc_len = (int) ((unsigned long) state->buffer + + state->buflen - (unsigned long) raw_desc); + + if (desc_len < sizeof(*desc) + desc->bNrInPins) { + usb_audio_err(state->chip, + "descriptor %d too short\n", + unitid); + return -EINVAL; + } err = uac_mixer_unit_get_channels(state, desc); if (err < 0) { -- 2.22.1