On Mon, Aug 14, 2023 at 06:05:59PM +0000, RD Babiera wrote:
> Some usb hubs will negotiate DisplayPort Alt mode with the device
> but will then negotiate a data role swap after entering the alt
> mode. The data role swap causes the device to unregister all alt
> modes, however the usb hub will still send Attention messages
> even after failing to reregister the Alt Mode. type_altmode_attention
> currently does not verify whether or not a device's altmode partner
> exists, which results in a NULL pointer error when dereferencing
> the typec_altmode and typec_altmode_ops belonging to the altmode
> partner.
>
> Verify the presence of a device's altmode partner before sending
> the Attention message to the Alt Mode driver.
>
> Fixes: 8a37d87d72f0 ("usb: typec: Bus type for alternate modes")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: RD Babiera <rdbabiera@xxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> Changes since v1:
> * Only assigns pdev if altmode partner exists in typec_altmode_attention
> * Removed error return in typec_altmode_attention if Alt Mode does
> not implement Attention messages.
> * Changed tcpm_log message to indicate that altmode partner does not exist,
> as it only logs in that case.
> ---
> Changes since v2:
> * Changed tcpm_log message to accurately reflect error
> * Revised commit message
> ---
> Changes since v3:
> * Fixed nits
> ---
> drivers/usb/typec/bus.c | 12 ++++++++++--
> drivers/usb/typec/tcpm/tcpm.c | 3 ++-
> include/linux/usb/typec_altmode.h | 2 +-
> 3 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/typec/bus.c b/drivers/usb/typec/bus.c
> index fe5b9a2e61f5..e95ec7e382bb 100644
> --- a/drivers/usb/typec/bus.c
> +++ b/drivers/usb/typec/bus.c
> @@ -183,12 +183,20 @@ EXPORT_SYMBOL_GPL(typec_altmode_exit);
> *
> * Notifies the partner of @adev about Attention command.
> */
> -void typec_altmode_attention(struct typec_altmode *adev, u32 vdo)
> +int typec_altmode_attention(struct typec_altmode *adev, u32 vdo)
> {
> - struct typec_altmode *pdev = &to_altmode(adev)->partner->adev;
> + struct altmode *partner = to_altmode(adev)->partner;
> + struct typec_altmode *pdev;
> +
> + if (!partner)
> + return -ENODEV;
> +
> + pdev = &partner->adev;
>
> if (pdev->ops && pdev->ops->attention)
> pdev->ops->attention(pdev, vdo);
> +
> + return 0;
> }
> EXPORT_SYMBOL_GPL(typec_altmode_attention);
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 5a7d8cc04628..77fe16190766 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -1877,7 +1877,8 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
> }
> break;
> case ADEV_ATTENTION:
> - typec_altmode_attention(adev, p[1]);
> + if (typec_altmode_attention(adev, p[1]))
> + tcpm_log(port, "typec_altmode_attention no port partner altmode");
> break;
> }
> }
> diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
> index 350d49012659..28aeef8f9e7b 100644
> --- a/include/linux/usb/typec_altmode.h
> +++ b/include/linux/usb/typec_altmode.h
> @@ -67,7 +67,7 @@ struct typec_altmode_ops {
>
> int typec_altmode_enter(struct typec_altmode *altmode, u32 *vdo);
> int typec_altmode_exit(struct typec_altmode *altmode);
> -void typec_altmode_attention(struct typec_altmode *altmode, u32 vdo);
> +int typec_altmode_attention(struct typec_altmode *altmode, u32 vdo);
> int typec_altmode_vdm(struct typec_altmode *altmode,
> const u32 header, const u32 *vdo, int count);
> int typec_altmode_notify(struct typec_altmode *altmode, unsigned long conf,
>
> base-commit: f176638af476c6d46257cc3303f5c7cf47d5967d
> --
> 2.41.0.694.ge786442a9b-goog
--
heikki
