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Date: Fri, 3 May 2024 01:18:35 +0000
From: Benson Leung <bleung@google.com>
To: Jameson Thies <jthies@google.com>
Cc: heikki.krogerus@linux.intel.com, linux-usb@vger.kernel.org,
	pmalani@chromium.org, abhishekpandit@chromium.org,
	andersson@kernel.org, dmitry.baryshkov@linaro.org,
	fabrice.gasnier@foss.st.com, gregkh@linuxfoundation.org,
	hdegoede@redhat.com, neil.armstrong@linaro.org,
	rajaram.regupathy@intel.com, saranya.gopal@intel.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/4] usb: typec: ucsi: Fix null pointer dereference in
 trace
Message-ID: <ZjQ7a8EGJlGTXX7W@google.com>
References: <20240503003920.1482447-1-jthies@google.com>
 <20240503003920.1482447-2-jthies@google.com>
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Hi Jameson,

On Fri, May 03, 2024 at 12:39:17AM +0000, Jameson Thies wrote:
> From: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
>=20
> ucsi_register_altmode checks IS_ERR on returned pointer and treats
> NULL as valid. When CONFIG_TYPEC_DP_ALTMODE is not enabled
> ucsi_register_displayport returns NULL which causese a NULL pointer
> dereference in trace. Rather than return NULL, call
> typec_port_register_altmode to register DisplayPort alternate mode
> as a non-controllable mode when CONFIG_TYPEC_DP_ALTMODE is not enabled.
>=20
> Reviewed-by: Jameson Thies <jthies@google.com>
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>

Reviewed-by: Benson Leung <bleung@chromium.org>

> ---
> Changes in V3:
> - Returns typec_port_register_altmode call from
> ucsi_register_displayport when CONFIG_TYPEC_DP_ALTMODE is not enabled.
>=20
> Changes in V2:
> - Checks for error response from ucsi_register_displayport when
> registering DisplayPort alternate mode.
>=20
>  drivers/usb/typec/ucsi/ucsi.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
> index c4d103db9d0f8..f66224a270bc6 100644
> --- a/drivers/usb/typec/ucsi/ucsi.h
> +++ b/drivers/usb/typec/ucsi/ucsi.h
> @@ -496,7 +496,7 @@ ucsi_register_displayport(struct ucsi_connector *con,
>  			  bool override, int offset,
>  			  struct typec_altmode_desc *desc)
>  {
> -	return NULL;
> +	return typec_port_register_altmode(con->port, desc);
>  }
> =20
>  static inline void
> --=20
> 2.45.0.rc1.225.g2a3ae87e7f-goog
>=20

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