Subject: FAILED: patch "[PATCH] HID: universal-pidff: stop the device when force-feedback" failed to apply to 6.6-stable tree
To: baul.lee@xbow.com,jkosina@suse.com
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Thu, 03 Sep 2026 15:28:57 +0200
Message-ID: <2026090357-math-destiny-2cbf@gregkh>
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The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x ce08c5555cabcd444d8b77fa69a7cb68bb05f611
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090357-math-destiny-2cbf@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ce08c5555cabcd444d8b77fa69a7cb68bb05f611 Mon Sep 17 00:00:00 2001
From: Baul Lee <baul.lee@xbow.com>
Date: Wed, 29 Jul 2026 23:24:32 +0900
Subject: [PATCH] HID: universal-pidff: stop the device when force-feedback
 init fails

universal_pidff_probe() starts the device with hid_hw_start() and then, if
force-feedback initialisation fails, returns the error through a label that
only does "return error".  The device is left started.

The HID core does not unwind on the driver's behalf.  __hid_device_probe()
releases the devres group, closes the report and clears hdev->driver:

	if (ret) {
		devres_release_group(&hdev->dev, hdev->devres_group_id);
		hid_close_report(hdev);
		hdev->driver = NULL;
	}

The hidraw character device that hid_hw_start() registered through
hid_connect() is allocated with kzalloc() and added with cdev_device_add(),
so it is not devres-managed and survives that.  With hdev->driver NULL,
hid_device_remove() skips hid_hw_stop() as well, because it only unwinds
while a driver is still attached.  The registration therefore outlives the
device on both paths.

Opening the surviving /dev/hidrawX writes into freed memory.  KASAN reports
a use-after-free write from hidraw_open() -> hid_hw_open() -> the
transport's open callback, which takes a spinlock inside the freed object.
A descriptor that carries a PID usage page and no input reports is enough:
hidraw claims the device so hid_hw_start() succeeds, while hid->inputs
stays empty so force-feedback init fails.  The other failure returns in
hid_pidff_init_with_quirks() - no output reports, an allocation failure,
pidff_init_fields(), pidff_check_autocenter(), an unusable effect count,
input_ff_create() - all reach the same label.

Stop the device on that path.  hid-dr.c and hid-emsff.c, which start the
device with the same HID_CONNECT_DEFAULT & ~HID_CONNECT_FF mask, already do
this.  The two earlier gotos must keep returning without hid_hw_stop(),
since neither has a started device, so give the path that fails after the
start its own label.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

Fixes: f06bf8d94fff ("HID: Add hid-universal-pidff driver and supported device ids")
Cc: stable@vger.kernel.org
Signed-off-by: Baul Lee <baul.lee@xbow.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/hid-universal-pidff.c b/drivers/hid/hid-universal-pidff.c
index 549dac555d40..60180467a0bf 100644
--- a/drivers/hid/hid-universal-pidff.c
+++ b/drivers/hid/hid-universal-pidff.c
@@ -104,12 +104,14 @@ static int universal_pidff_probe(struct hid_device *hdev,
 	error = init_function(hdev, id->driver_data);
 	if (error) {
 		hid_warn(hdev, "Error initialising force feedback\n");
-		goto err;
+		goto err_stop;
 	}
 
 	hid_info(hdev, "Universal pidff driver loaded successfully!");
 
 	return 0;
+err_stop:
+	hid_hw_stop(hdev);
 err:
 	return error;
 }