From 2905281cbda52ec9df540113b35b835feb5fafd3 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 20 Apr 2026 18:00:27 +0200 Subject: [PATCH] Input: usbtouchscreen - clamp NEXIO data_len/x_len to URB buffer size MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit nexio_read_data() pulls data_len and x_len from a packed __be16 header in the device's interrupt packet and then walks packet->data[0..x_len) and packet->data[x_len..data_len) comparing each byte against a threshold. Both fields are 16-bit on the wire (max 65535). The existing adjustments shave at most 0x100 / 0x80 off, so the loop bound can still reach roughly 0xfeff. The URB transfer buffer for NEXIO is rept_size (1024) bytes from usb_alloc_coherent(), with the first 7 occupied by the packed header — so packet->data[] has 1017 valid bytes. read_data() callbacks are not given urb->actual_length, and nothing else bounds the walk. A device that lies about its length can get a ~64 KiB out-of-bounds read past the coherent DMA allocation. The first index whose byte exceeds NEXIO_THRESHOLD lands in begin_x / begin_y and from there into the reported touch coordinates, so adjacent kernel memory contents leak to userspace as ABS_X / ABS_Y events. Far enough out, the read can also hit an unmapped page and fault. Fix this all by clamping data_len to the buffer's data[] capacity and x_len to data_len. Cc: Dmitry Torokhov Fixes: 5197424cdccc ("Input: usbtouchscreen - add NEXIO (or iNexio) support") Cc: stable Assisted-by: gkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman Link: https://patch.msgid.link/2026042026-chlorine-epidermis-fd6d@gregkh Signed-off-by: Dmitry Torokhov --- drivers/input/touchscreen/usbtouchscreen.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c index daa28135f887..0bbacb517c28 100644 --- a/drivers/input/touchscreen/usbtouchscreen.c +++ b/drivers/input/touchscreen/usbtouchscreen.c @@ -1067,6 +1067,11 @@ static int nexio_read_data(struct usbtouch_usb *usbtouch, unsigned char *pkt) if (x_len > 0xff) x_len -= 0x80; + if (data_len > usbtouch->data_size - sizeof(*packet)) + data_len = usbtouch->data_size - sizeof(*packet); + if (x_len > data_len) + x_len = data_len; + /* send ACK */ ret = usb_submit_urb(priv->ack, GFP_ATOMIC); if (ret)