From: Jiale Yao Date: Sat, 25 Jul 2026 16:27:51 +0000 (+0800) Subject: USB: serial: option: fix slab OOB read in interrupt URB callback X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2ef5560387f2c0713cee975be2b24b281bd90f3e;p=linux USB: serial: option: fix slab OOB read in interrupt URB callback commit 885d802f544ca7bfa8f3984d94233cce715bb6b3 upstream. The interrupt URB buffer is allocated in setup_port_interrupt_in() based on the endpoint's wMaxPacketSize: buffer_size = usb_endpoint_maxp(epd); port->interrupt_in_buffer = kmalloc(buffer_size, GFP_KERNEL); When a USB device declares wMaxPacketSize = 8 on its interrupt IN endpoint, the buffer is allocated from kmalloc-8 cache (exactly 8 bytes). If the device sends a short packet (actual_length < wMaxPacketSize), the URB completes with status == 0 and the callback proceeds to read: data[sizeof(struct usb_ctrlrequest)] which evaluates to data[8], accessing 1 byte beyond the allocated 8-byte buffer. This results in a slab out-of-bounds read. Fix this by adding the missing bounds check: first verify that the actual length is large enough to contain the struct usb_ctrlrequest header before accessing req_pkt->bRequestType and req_pkt->bRequest, and then verify that there is an additional byte for the modem signal state before reading data[sizeof(struct usb_ctrlrequest)] inside the conditional. Use sizeof(*req_pkt) instead of sizeof(struct usb_ctrlrequest) for consistency. Assisted-by: Claude:deepseek-v4-pro Signed-off-by: Jiale Yao Fixes: 58cfe9113e48 ("[PATCH] USB: add Option Card driver") Cc: stable@vger.kernel.org # v2.6.12 [ johan: use dev_err(); split signals declaration and initialisation ] Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c index 89624f38fec2e..5652155fc680b 100644 --- a/drivers/usb/serial/option.c +++ b/drivers/usb/serial/option.c @@ -2690,12 +2690,26 @@ static void option_instat_callback(struct urb *urb) dev_dbg(dev, "%s: NULL req_pkt\n", __func__); return; } + + if (urb->actual_length < sizeof(*req_pkt)) { + dev_err(dev, "%s: short packet: %u bytes\n", __func__, + urb->actual_length); + return; + } + if ((req_pkt->bRequestType == 0xA1) && (req_pkt->bRequest == 0x20)) { + unsigned char signals; int old_dcd_state; - unsigned char signals = *((unsigned char *) - urb->transfer_buffer + - sizeof(struct usb_ctrlrequest)); + + if (urb->actual_length < sizeof(*req_pkt) + 1) { + dev_err(dev, "%s: short interrupt transfer: %u bytes\n", + __func__, urb->actual_length); + return; + } + + signals = *((unsigned char *)urb->transfer_buffer + + sizeof(*req_pkt)); dev_dbg(dev, "%s: signal x%x\n", __func__, signals);