On Tue, Oct 07, 2025 at 05:41:32PM -0400, pip-izony wrote:

From: Seungjin Bae eeodqql09@gmail.com

In the pegasus_notetaker driver, the pegasus_probe() function allocates the URB transfer buffer using the wMaxPacketSize value from the endpoint descriptor. An attacker can use a malicious USB descriptor to force the allocation of a very small buffer.

Subsequently, if the device sends an interrupt packet with a specific pattern (e.g., where the first byte is 0x80 or 0x42), the pegasus_parse_packet() function parses the packet without checking the allocated buffer size. This leads to an out-of-bounds memory access, which could result in a system panic.

Fixes: 948bf18 ("Input: remove third argument of usb_maxpacket()") Signed-off-by: Seungjin Bae eeodqql09@gmail.com

---

drivers/input/tablet/pegasus_notetaker.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/drivers/input/tablet/pegasus_notetaker.c b/drivers/input/tablet/pegasus_notetaker.c index 8d6b71d59793..6c4199712a4e 100644 --- a/drivers/input/tablet/pegasus_notetaker.c +++ b/drivers/input/tablet/pegasus_notetaker.c @@ -311,6 +311,11 @@ static int pegasus_probe(struct usb_interface *intf, } pegasus->data_len = usb_maxpacket(dev, pipe);

• if (pegasus->data_len < 5) {

• dev_err(&intf->dev, "Invalid number of wMaxPacketSize\n");
  

• error = -EINVAL;
  

• goto err_free_mem;
  

• }

pegasus->data = usb_alloc_coherent(dev, pegasus->data_len, GFP_KERNEL, &pegasus->data_dma); -- 2.43.0

<formletter>

This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.

</formletter>