linux-kernel - [PATCH] Input: pegasus-notetaker - fix out-of-bounds access vulnerability in pegasus_parse

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Message-ID: <20251007214131.3737115-2-eeodqql09@gmail.com>
Date: Tue,  7 Oct 2025 17:41:32 -0400
From: pip-izony <eeodqql09@...il.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Seungjin Bae <eeodqql09@...il.com>,
	Kyungtae Kim <Kyungtae.Kim@...tmouth.edu>,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] Input: pegasus-notetaker - fix out-of-bounds access vulnerability in pegasus_parse_packet() function of the pegasus driver

From: Seungjin Bae <eeodqql09@...il.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@...il.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