linux-kernel - [PATCH] most: usb: fix double free on late probe failure

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Message-ID: <20251029093029.28922-1-johan@kernel.org>
Date: Wed, 29 Oct 2025 10:30:29 +0100
From: Johan Hovold <johan@...nel.org>
To: Parthiban Veerasooran <parthiban.veerasooran@...rochip.com>,
	Christian Gromm <christian.gromm@...rochip.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Victoria Votokina <Victoria.Votokina@...persky.com>,
	linux-kernel@...r.kernel.org,
	Johan Hovold <johan@...nel.org>,
	stable@...r.kernel.org
Subject: [PATCH] most: usb: fix double free on late probe failure

The MOST subsystem has a non-standard registration function which frees
the interface on registration failures and on deregistration.

This unsurprisingly leads to bugs in the MOST drivers, and a couple of
recent changes turned a reference underflow and use-after-free in the
USB driver into several double free and a use-after-free on late probe
failures.

Fixes: 723de0f9171e ("staging: most: remove device from interface structure")
Fixes: 4b1270902609 ("most: usb: Fix use-after-free in hdm_disconnect")
Fixes: a8cc9e5fcb0e ("most: usb: hdm_probe: Fix calling put_device() before device initialization")
Cc: stable@...r.kernel.org
Cc: Christian Gromm <christian.gromm@...rochip.com>
Cc: Victoria Votokina <Victoria.Votokina@...persky.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/most/most_usb.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/most/most_usb.c b/drivers/most/most_usb.c
index 10064d7b7249..41ee169f80c5 100644
--- a/drivers/most/most_usb.c
+++ b/drivers/most/most_usb.c
@@ -1058,7 +1058,7 @@ hdm_probe(struct usb_interface *interface, const struct usb_device_id *id)
 
 	ret = most_register_interface(&mdev->iface);
 	if (ret)
-		goto err_free_busy_urbs;
+		return ret;
 
 	mutex_lock(&mdev->io_mutex);
 	if (le16_to_cpu(usb_dev->descriptor.idProduct) == USB_DEV_ID_OS81118 ||
@@ -1068,8 +1068,7 @@ hdm_probe(struct usb_interface *interface, const struct usb_device_id *id)
 		if (!mdev->dci) {
 			mutex_unlock(&mdev->io_mutex);
 			most_deregister_interface(&mdev->iface);
-			ret = -ENOMEM;
-			goto err_free_busy_urbs;
+			return -ENOMEM;
 		}
 
 		mdev->dci->dev.init_name = "dci";
@@ -1078,18 +1077,15 @@ hdm_probe(struct usb_interface *interface, const struct usb_device_id *id)
 		mdev->dci->dev.release = release_dci;
 		if (device_register(&mdev->dci->dev)) {
 			mutex_unlock(&mdev->io_mutex);
+			put_device(&mdev->dci->dev);
 			most_deregister_interface(&mdev->iface);
-			ret = -ENOMEM;
-			goto err_free_dci;
+			return -ENOMEM;
 		}
 		mdev->dci->usb_device = mdev->usb_device;
 	}
 	mutex_unlock(&mdev->io_mutex);
 	return 0;
-err_free_dci:
-	put_device(&mdev->dci->dev);
-err_free_busy_urbs:
-	kfree(mdev->busy_urbs);
+
 err_free_ep_address:
 	kfree(mdev->ep_address);
 err_free_cap:
-- 
2.51.0