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Wed, 17 Jun 2026 23:03:24 -0700 (PDT) From: Maoyi Xie To: Daniel Mack , Jaroslav Kysela , Takashi Iwai Cc: linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] ALSA: caiaq: bound the length in the EP1 input parsers Date: Thu, 18 Jun 2026 14:03:15 +0800 Message-ID: <178176259547.3343534.6659489917322808916@maoyixie.com> In-Reply-To: <178176259547.3343534.6658931377288378506@maoyixie.com> References: <178176259547.3343534.6658931377288378506@maoyixie.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 snd_caiaq_input_read_erp() and snd_caiaq_input_read_io() can be reached from snd_usb_caiaq_input_dispatch(). They read fixed byte offsets from the reply buffer without checking the reported length. On a short reply they decode stale bytes left from a previous, longer report and feed them to the input layer. This is not an out-of-bounds access. Every offset is a compile-time driver constant. The largest is buf[21] in the Maschine ERP case. The EP1 transfer buffer ep1_in_buf is EP1_BUFSIZE (64) bytes, and the USB core caps actual_length at 64, so a short reply only reads in-bounds stale data. Acting on data the device did not send is still wrong, so bail out per usb_id case when the reply is shorter than the bytes that case consumes. read_erp: AK1 needs 2 bytes, Kore needs 16, Maschine needs 22. read_io: the Kore case needs 5 bytes (buf[4]) and the Traktor Kontrol X1 case needs 7 (buf[5]/buf[6]). The preceding key bit loop is already bounded by "i < len * 8" and is left untouched. snd_caiaq_input_read_analog() and snd_usb_caiaq_maschine_dispatch() are not changed. Their callers already floor the reply length. Suggested-by: Takashi Iwai Signed-off-by: Maoyi Xie --- sound/usb/caiaq/input.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/sound/usb/caiaq/input.c b/sound/usb/caiaq/input.c index 2db4d1332df1..eabbf41fdfb2 100644 --- a/sound/usb/caiaq/input.c +++ b/sound/usb/caiaq/input.c @@ -237,12 +237,16 @@ static void snd_caiaq_input_read_erp(struct snd_usb_caiaqdev *cdev, switch (cdev->chip.usb_id) { case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_AK1): + if (len < 2) + return; i = decode_erp(buf[0], buf[1]); input_report_abs(input_dev, ABS_X, i); input_sync(input_dev); break; case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_KORECONTROLLER): case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_KORECONTROLLER2): + if (len < 16) + return; i = decode_erp(buf[7], buf[5]); input_report_abs(input_dev, ABS_HAT0X, i); i = decode_erp(buf[12], buf[14]); @@ -263,6 +267,8 @@ static void snd_caiaq_input_read_erp(struct snd_usb_caiaqdev *cdev, break; case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_MASCHINECONTROLLER): + if (len < 22) + return; /* 4 under the left screen */ input_report_abs(input_dev, ABS_HAT0X, decode_erp(buf[21], buf[20])); input_report_abs(input_dev, ABS_HAT0Y, decode_erp(buf[15], buf[14])); @@ -308,9 +314,13 @@ static void snd_caiaq_input_read_io(struct snd_usb_caiaqdev *cdev, switch (cdev->chip.usb_id) { case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_KORECONTROLLER): case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_KORECONTROLLER2): + if (len < 5) + return; input_report_abs(cdev->input_dev, ABS_MISC, 255 - buf[4]); break; case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_TRAKTORKONTROLX1): + if (len < 7) + return; /* rotary encoders */ input_report_abs(cdev->input_dev, ABS_X, buf[5] & 0xf); input_report_abs(cdev->input_dev, ABS_Y, buf[5] >> 4); -- 2.34.1