linux-kernel - Re: [PATCH v2 1/4] usb: typec: ucsi: Fix null deref in trace

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Message-ID: <32855f4c-f219-4396-81c3-42cbea9fe4da@moroto.mountain>
Date: Tue, 30 Apr 2024 10:17:59 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Jameson Thies <jthies@...gle.com>
Cc: heikki.krogerus@...ux.intel.com, linux-usb@...r.kernel.org,
	pmalani@...omium.org, bleung@...gle.com,
	abhishekpandit@...omium.org, andersson@...nel.org,
	dmitry.baryshkov@...aro.org, fabrice.gasnier@...s.st.com,
	gregkh@...uxfoundation.org, hdegoede@...hat.com,
	neil.armstrong@...aro.org, rajaram.regupathy@...el.com,
	saranya.gopal@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] usb: typec: ucsi: Fix null deref in trace

On Wed, Apr 24, 2024 at 01:48:18AM +0000, Jameson Thies wrote:
> From: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> 
> ucsi_register_altmode checks IS_ERR on returned pointer and treats
> NULL as valid. This results in a null deref when
> trace_ucsi_register_altmode is called. Return an error from
> ucsi_register_displayport when it is not supported and register the
> altmode with typec_port_register_altmode.
> 
> Reviewed-by: Jameson Thies <jthies@...gle.com>
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>

This is not the correct way to fix this.  The normal thing to do would
be to add NULL checks.

https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/'

regards,
dan carpenter