linux-kernel - [PATCH v4] Bluetooth: bfusb: Fix buffer over-read in rx processing loop

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Message-ID: <20251009164817.3762787-2-eeodqql09@gmail.com>
Date: Thu,  9 Oct 2025 12:48:18 -0400
From: pip-izony <eeodqql09@...il.com>
To: Marcel Holtmann <marcel@...tmann.org>
Cc: Seungjin Bae <eeodqql09@...il.com>,
	Kyungtae Kim <Kyungtae.Kim@...tmouth.edu>,
	Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-bluetooth@...r.kernel.org
Subject: [PATCH v4] Bluetooth: bfusb: Fix buffer over-read in rx processing loop

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

The bfusb_rx_complete() function parses incoming URB data in a while loop.
The logic does not sufficiently validate the remaining buffer size(count)
across loop iterations, which can lead to a buffer over-read.

For example, with 4-bytes remaining buffer, if the first iteration takes
the `hdr & 0x4000` branch, 2-bytes are consumed. On the next iteration,
only 2-bytes remain, but the else branch is trying to access the third
byte(buf[2]). This causes an out-of-bounds read and a potential kernel
panic.

This patch fixes the vulnerability by adding checks to ensure enough
data remains in the buffer before it is accessed.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Seungjin Bae <eeodqql09@...il.com>
---
  v1 -> v2: Fixing the error function name
  v2 -> v3: Addressing feedback from Paul Menzel
  v3 -> v4: Improving the error message for the block header count

 drivers/bluetooth/bfusb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/bluetooth/bfusb.c b/drivers/bluetooth/bfusb.c
index 8df310983bf6..02ba16775004 100644
--- a/drivers/bluetooth/bfusb.c
+++ b/drivers/bluetooth/bfusb.c
@@ -360,6 +360,11 @@ static void bfusb_rx_complete(struct urb *urb)
 			count -= 2;
 			buf   += 2;
 		} else {
+			if (count < 3) {
+				bt_dev_err(data->hdev, "block header count %d < 3 (too short)",
+					   count);
+				break;
+			}
 			len = (buf[2] == 0) ? 256 : buf[2];
 			count -= 3;
 			buf   += 3;
-- 
2.43.0