linux-kernel - Re: [PATCH v3] HID: hid-ntrig: fix unable to handle page fault in ntrig_report

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Message-ID: <20250813092234.ja5qfpvkxocfnchd@minbellkim-500TGA-500SGA>
Date: Wed, 13 Aug 2025 18:22:34 +0900
From: Minjong Kim <minbell.kim@...sung.com>
To: Benjamin Tissoires <bentiss@...nel.org>
Cc: Jiri Kosina <jikos@...nel.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] HID: hid-ntrig: fix unable to handle page fault in
 ntrig_report_version()

On Wed, Aug 13, 2025 at 10:39:37AM +0200, Benjamin Tissoires wrote:
> On Aug 13 2025, Minjong Kim wrote:
> > 
> > From 75e52defd4b2fd138285c5ad953942e2e6cf2fbb Mon Sep 17 00:00:00 2001
> > From: Minjong Kim <minbell.kim@...sung.com>
> > Date: Thu, 17 Jul 2025 14:37:47 +0900
> > Subject: [PATCH v2] HID: hid-ntrig: fix unable to handle page fault in
> >  ntrig_report_version()
> > 
> > in ntrig_report_version(), hdev parameter passed from hid_probe().
> > sending descriptor to /dev/uhid can make hdev->dev.parent->parent to null
> > if hdev->dev.parent->parent is null, usb_dev has
> > invalid address(0xffffffffffffff58) that hid_to_usb_dev(hdev) returned
> > when usb_rcvctrlpipe() use usb_dev,it trigger
> > page fault error for address(0xffffffffffffff58)
> > 
> > add null check logic to ntrig_report_version()
> > before calling hid_to_usb_dev()
> > 
> > Signed-off-by: Minjong Kim <minbell.kim@...sung.com>
> > ---
> >  drivers/hid/hid-ntrig.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/hid/hid-ntrig.c b/drivers/hid/hid-ntrig.c
> > index 2738ce947434..fa948d9e236c 100644
> > --- a/drivers/hid/hid-ntrig.c
> > +++ b/drivers/hid/hid-ntrig.c
> > @@ -144,6 +144,9 @@ static void ntrig_report_version(struct hid_device *hdev)
> >  	struct usb_device *usb_dev = hid_to_usb_dev(hdev);
> >  	unsigned char *data = kmalloc(8, GFP_KERNEL);
> > 
> > +	if (!hdev->dev.parent->parent)
> 
> Why simply not use if(!hid_is_usb(hdev)) instead?
> 
> Cheers,
> Benjamin
>

>From 61818c85614ad40beab53cee421272814576836d Mon Sep 17 00:00:00 2001
From: Minjong Kim <minbell.kim@...sung.com>
Date: Thu, 17 Jul 2025 14:37:47 +0900
Subject: [PATCH v3] HID: hid-ntrig: fix unable to handle page fault in
 ntrig_report_version()

in ntrig_report_version(), hdev parameter passed from hid_probe().
sending descriptor to /dev/uhid can make hdev->dev.parent->parent to null
if hdev->dev.parent->parent is null, usb_dev has
invalid address(0xffffffffffffff58) that hid_to_usb_dev(hdev) returned
when usb_rcvctrlpipe() use usb_dev,it trigger
page fault error for address(0xffffffffffffff58)

add null check logic to ntrig_report_version()
before calling hid_to_usb_dev()

Signed-off-by: Minjong Kim <minbell.kim@...sung.com>
---
 drivers/hid/hid-ntrig.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-ntrig.c b/drivers/hid/hid-ntrig.c
index 2738ce947434..0f76e241e0af 100644
--- a/drivers/hid/hid-ntrig.c
+++ b/drivers/hid/hid-ntrig.c
@@ -144,6 +144,9 @@ static void ntrig_report_version(struct hid_device *hdev)
 	struct usb_device *usb_dev = hid_to_usb_dev(hdev);
 	unsigned char *data = kmalloc(8, GFP_KERNEL);
 
+	if (!hid_is_usb(hdev))
+		return;
+
 	if (!data)
 		goto err_free;
 
-- 
2.34.1


I checked that crashes didn't occuered this patch
then, I'm just wondering why it is effective?
could you explain me about this?

Best regards,