From 52f2ad3f7e5eb3b5908e1d685d4342519dc9cfcd Mon Sep 17 00:00:00 2001 From: Heitor Alves de Siqueira Date: Tue, 5 May 2026 15:56:03 -0300 Subject: [PATCH] usb: usbtmc: check URB actual_length for interrupt-IN notifications USBTMC devices can use an optional interrupt endpoint for notification messages. These typically contain two-byte headers indicating the payload format, but the driver does not check if these headers are present before accessing the data buffers. In cases where the URB actual_length is not enough to fit these headers, the driver will either cause an out-of-bounds read, or consume stale leftover data from a previous notification. Fix by checking if actual_data contains enough bytes for the headers, otherwise resubmit URB to the interrupt endpoint. Fixes: dbf3e7f654c0 ("Implement an ioctl to support the USMTMC-USB488 READ_STATUS_BYTE operation.") Reported-by: syzbot+abbfd103085885cf16a2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=abbfd103085885cf16a2 Cc: stable Suggested-by: Michal Pecio Signed-off-by: Heitor Alves de Siqueira Link: https://patch.msgid.link/20260505-usbtmc-iin-size-v3-1-a36113f62db7@igalia.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/usbtmc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c index bd9347804dec..e15efd0c5ca7 100644 --- a/drivers/usb/class/usbtmc.c +++ b/drivers/usb/class/usbtmc.c @@ -2306,6 +2306,14 @@ static void usbtmc_interrupt(struct urb *urb) switch (status) { case 0: /* SUCCESS */ + /* ensure at least two bytes of headers were transferred */ + if (urb->actual_length < 2) { + dev_warn(dev, + "actual length %d not sufficient for interrupt headers\n", + urb->actual_length); + goto exit; + } + /* check for valid STB notification */ if (data->iin_buffer[0] > 0x81) { data->bNotify1 = data->iin_buffer[0];