linux-kernel - Re: [PATCH v3] usb: typec: tcpm: Check for port partner validity before consuming it

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Message-ID: <Zi9aLJS2vlHxwaFP@kuha.fi.intel.com>
Date: Mon, 29 Apr 2024 11:28:28 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Badhri Jagan Sridharan <badhri@...gle.com>
Cc: gregkh@...uxfoundation.org, linux@...ck-us.net, kyletso@...gle.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	rdbabiera@...gle.com, amitsd@...gle.com, stable@...r.kernel.org,
	frank.wang@...k-chips.com, broonie@...nel.org,
	dmitry.baryshkov@...aro.org
Subject: Re: [PATCH v3] usb: typec: tcpm: Check for port partner validity
 before consuming it

On Sat, Apr 27, 2024 at 08:28:12PM +0000, Badhri Jagan Sridharan wrote:
> typec_register_partner() does not guarantee partner registration
> to always succeed. In the event of failure, port->partner is set
> to the error value or NULL. Given that port->partner validity is
> not checked, this results in the following crash:
> 
> Unable to handle kernel NULL pointer dereference at virtual address xx
>  pc : run_state_machine+0x1bc8/0x1c08
>  lr : run_state_machine+0x1b90/0x1c08
> ..
>  Call trace:
>    run_state_machine+0x1bc8/0x1c08
>    tcpm_state_machine_work+0x94/0xe4
>    kthread_worker_fn+0x118/0x328
>    kthread+0x1d0/0x23c
>    ret_from_fork+0x10/0x20
> 
> To prevent the crash, check for port->partner validity before
> derefencing it in all the call sites.
> 
> Cc: stable@...r.kernel.org
> Fixes: c97cd0b4b54e ("usb: typec: tcpm: set initial svdm version based on pd revision")
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/usb/typec/tcpm/tcpm.c | 30 +++++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index ab6ed6111ed0..e1c6dffe5f8b 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1580,7 +1580,8 @@ static void svdm_consume_identity(struct tcpm_port *port, const u32 *p, int cnt)
>  	port->partner_ident.cert_stat = p[VDO_INDEX_CSTAT];
>  	port->partner_ident.product = product;
>  
> -	typec_partner_set_identity(port->partner);
> +	if (port->partner)
> +		typec_partner_set_identity(port->partner);
>  
>  	tcpm_log(port, "Identity: %04x:%04x.%04x",
>  		 PD_IDH_VID(vdo),
> @@ -1742,6 +1743,9 @@ static void tcpm_register_partner_altmodes(struct tcpm_port *port)
>  	struct typec_altmode *altmode;
>  	int i;
>  
> +	if (!port->partner)
> +		return;
> +
>  	for (i = 0; i < modep->altmodes; i++) {
>  		altmode = typec_partner_register_altmode(port->partner,
>  						&modep->altmode_desc[i]);
> @@ -4231,7 +4235,10 @@ static int tcpm_init_vconn(struct tcpm_port *port)
>  
>  static void tcpm_typec_connect(struct tcpm_port *port)
>  {
> +	struct typec_partner *partner;
> +
>  	if (!port->connected) {
> +		port->connected = true;
>  		/* Make sure we don't report stale identity information */
>  		memset(&port->partner_ident, 0, sizeof(port->partner_ident));
>  		port->partner_desc.usb_pd = port->pd_capable;
> @@ -4241,9 +4248,13 @@ static void tcpm_typec_connect(struct tcpm_port *port)
>  			port->partner_desc.accessory = TYPEC_ACCESSORY_AUDIO;
>  		else
>  			port->partner_desc.accessory = TYPEC_ACCESSORY_NONE;
> -		port->partner = typec_register_partner(port->typec_port,
> -						       &port->partner_desc);
> -		port->connected = true;
> +		partner = typec_register_partner(port->typec_port, &port->partner_desc);
> +		if (IS_ERR(partner)) {
> +			dev_err(port->dev, "Failed to register partner (%ld)\n", PTR_ERR(partner));
> +			return;
> +		}
> +
> +		port->partner = partner;
>  		typec_partner_set_usb_power_delivery(port->partner, port->partner_pd);
>  	}
>  }
> @@ -4323,9 +4334,11 @@ static void tcpm_typec_disconnect(struct tcpm_port *port)
>  	port->plug_prime = NULL;
>  	port->cable = NULL;
>  	if (port->connected) {
> -		typec_partner_set_usb_power_delivery(port->partner, NULL);
> -		typec_unregister_partner(port->partner);
> -		port->partner = NULL;
> +		if (port->partner) {
> +			typec_partner_set_usb_power_delivery(port->partner, NULL);
> +			typec_unregister_partner(port->partner);
> +			port->partner = NULL;
> +		}
>  		port->connected = false;
>  	}
>  }
> @@ -4549,6 +4562,9 @@ static enum typec_cc_status tcpm_pwr_opmode_to_rp(enum typec_pwr_opmode opmode)
>  
>  static void tcpm_set_initial_svdm_version(struct tcpm_port *port)
>  {
> +	if (!port->partner)
> +		return;
> +
>  	switch (port->negotiated_rev) {
>  	case PD_REV30:
>  		break;
> 
> base-commit: 3f12222a4bebeb13ce06ddecc1610ad32fa835dd
> -- 
> 2.44.0.769.g3c40516874-goog

-- 
heikki