There is no good reason to support those, no physical device will ever
produce those. Allowing \n in phys previously triggered CVE-2026-50292
in libinput - there the PHYS udev property value was used as part of
another udev property value. The linebreak then caused the property
to be split across two lines, allowing uinput devices to inject
malicious properties. While the bug is squarely inlibinput's court
there still isn't a good reason for control characters in uinput/uhid.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
---
 drivers/hid/uhid.c          |  1 +
 drivers/input/misc/uinput.c |  1 +
 include/linux/input.h       | 15 +++++++++++++++
 3 files changed, 17 insertions(+)

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 37b60c3aaf66..baf1fe8290f7 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -513,16 +513,17 @@ static int uhid_dev_create2(struct uhid_device *uhid,
 		ret = PTR_ERR(hid);
 		goto err_free;
 	}
 
 	BUILD_BUG_ON(sizeof(hid->name) != sizeof(ev->u.create2.name));
 	strscpy(hid->name, ev->u.create2.name, sizeof(hid->name));
 	BUILD_BUG_ON(sizeof(hid->phys) != sizeof(ev->u.create2.phys));
 	strscpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
+	input_sanitize_phys(hid->phys);
 	BUILD_BUG_ON(sizeof(hid->uniq) != sizeof(ev->u.create2.uniq));
 	strscpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));
 
 	hid->ll_driver = &uhid_hid_driver;
 	hid->bus = ev->u.create2.bus;
 	hid->vendor = ev->u.create2.vendor;
 	hid->product = ev->u.create2.product;
 	hid->version = ev->u.create2.version;
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index d32fa4b508fc..70fe4f3e73bf 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -998,16 +998,17 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
 
 		phys = strndup_user(p, 1024);
 		if (IS_ERR(phys)) {
 			retval = PTR_ERR(phys);
 			goto out;
 		}
 
 		kfree(udev->dev->phys);
+		input_sanitize_phys(phys);
 		udev->dev->phys = phys;
 		goto out;
 
 	case UI_BEGIN_FF_UPLOAD:
 		retval = uinput_ff_upload_from_user(p, &ff_up);
 		if (retval)
 			goto out;
 
diff --git a/include/linux/input.h b/include/linux/input.h
index 76f7aa226202..6c182f5c783f 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -527,16 +527,31 @@ int input_set_keycode(struct input_dev *dev,
 
 bool input_match_device_id(const struct input_dev *dev,
 			   const struct input_device_id *id);
 
 void input_enable_softrepeat(struct input_dev *dev, int delay, int period);
 
 bool input_device_enabled(struct input_dev *dev);
 
+/**
+ * input_sanitize_phys - replace invalid characters in a phys string
+ * @phys: the phys path to sanitize (modified in place)
+ *
+ * Replaces any control characters and non-ASCII characters with '?'.
+ **/
+static inline void input_sanitize_phys(char *phys)
+{
+	char *p;
+
+	for (p = phys; *p; p++)
+		if (*p < 0x20 || *p > 0x7e)
+			*p = '?';
+}
+
 extern const struct class input_class;
 
 /**
  * struct ff_device - force-feedback part of an input device
  * @upload: Called to upload an new effect into device
  * @erase: Called to erase an effect from device
  * @playback: Called to request device to start playing specified effect
  * @set_gain: Called to set specified gain

---
base-commit: 58717b2a1365d06c8c64b72aa948541b53fe31eb
change-id: 20260717-wip-uinput-sanitize-phys-abb6cf40e577

Best regards,
-- 
Peter Hutterer <peter.hutterer@who-t.net>

Hi Peter!

On Fri, Jul 17, 2026, at 6:49 AM, Peter Hutterer wrote:
> There is no good reason to support those, no physical device will ever
> produce those. Allowing \n in phys previously triggered CVE-2026-50292
> in libinput - there the PHYS udev property value was used as part of
> another udev property value. The linebreak then caused the property
> to be split across two lines, allowing uinput devices to inject
> malicious properties. While the bug is squarely inlibinput's court
> there still isn't a good reason for control characters in uinput/uhid.
>
> Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
> ---
>  drivers/hid/uhid.c          |  1 +
>  drivers/input/misc/uinput.c |  1 +
>  include/linux/input.h       | 15 +++++++++++++++
>  3 files changed, 17 insertions(+)
>
> diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
> index 37b60c3aaf66..baf1fe8290f7 100644
> --- a/drivers/hid/uhid.c
> +++ b/drivers/hid/uhid.c
> @@ -513,16 +513,17 @@ static int uhid_dev_create2(struct uhid_device *uhid,
>  		ret = PTR_ERR(hid);
>  		goto err_free;
>  	}
> 
>  	BUILD_BUG_ON(sizeof(hid->name) != sizeof(ev->u.create2.name));
>  	strscpy(hid->name, ev->u.create2.name, sizeof(hid->name));
>  	BUILD_BUG_ON(sizeof(hid->phys) != sizeof(ev->u.create2.phys));
>  	strscpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
> +	input_sanitize_phys(hid->phys);
>  	BUILD_BUG_ON(sizeof(hid->uniq) != sizeof(ev->u.create2.uniq));
>  	strscpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));
> 
>  	hid->ll_driver = &uhid_hid_driver;
>  	hid->bus = ev->u.create2.bus;
>  	hid->vendor = ev->u.create2.vendor;
>  	hid->product = ev->u.create2.product;
>  	hid->version = ev->u.create2.version;
> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
> index d32fa4b508fc..70fe4f3e73bf 100644
> --- a/drivers/input/misc/uinput.c
> +++ b/drivers/input/misc/uinput.c
> @@ -998,16 +998,17 @@ static long uinput_ioctl_handler(struct file 
> *file, unsigned int cmd,
> 
>  		phys = strndup_user(p, 1024);
>  		if (IS_ERR(phys)) {
>  			retval = PTR_ERR(phys);
>  			goto out;
>  		}
> 
>  		kfree(udev->dev->phys);
> +		input_sanitize_phys(phys);
>  		udev->dev->phys = phys;
>  		goto out;
> 
>  	case UI_BEGIN_FF_UPLOAD:
>  		retval = uinput_ff_upload_from_user(p, &ff_up);
>  		if (retval)
>  			goto out;
> 
> diff --git a/include/linux/input.h b/include/linux/input.h
> index 76f7aa226202..6c182f5c783f 100644
> --- a/include/linux/input.h
> +++ b/include/linux/input.h
> @@ -527,16 +527,31 @@ int input_set_keycode(struct input_dev *dev,
> 
>  bool input_match_device_id(const struct input_dev *dev,
>  			   const struct input_device_id *id);
> 
>  void input_enable_softrepeat(struct input_dev *dev, int delay, int period);
> 
>  bool input_device_enabled(struct input_dev *dev);
> 
> +/**
> + * input_sanitize_phys - replace invalid characters in a phys string
> + * @phys: the phys path to sanitize (modified in place)
> + *
> + * Replaces any control characters and non-ASCII characters with '?'.
> + **/
> +static inline void input_sanitize_phys(char *phys)
> +{
> +	char *p;
> +
> +	for (p = phys; *p; p++)
> +		if (*p < 0x20 || *p > 0x7e)
> +			*p = '?';
> +}
> +

Reviewed-by: David Rheinsberg <david@readahead.eu>

I would also be fine to just reject them in uinput, but I guess this is the less intrusive option.

Thanks a lot!
David

>  extern const struct class input_class;
> 
>  /**
>   * struct ff_device - force-feedback part of an input device
>   * @upload: Called to upload an new effect into device
>   * @erase: Called to erase an effect from device
>   * @playback: Called to request device to start playing specified effect
>   * @set_gain: Called to set specified gain
>
> ---
> base-commit: 58717b2a1365d06c8c64b72aa948541b53fe31eb
> change-id: 20260717-wip-uinput-sanitize-phys-abb6cf40e577
>
> Best regards,
> -- 
> Peter Hutterer <peter.hutterer@who-t.net>