On Tue, Apr 29, 2025 at 11:49:08PM +0000, RD Babiera wrote:
> A state check was previously added to tcpm_queue_vdm_unlocked to
> prevent a deadlock where the DisplayPort Alt Mode driver would be
> executing work and attempting to grab the tcpm_lock while the TCPM
> was holding the lock and attempting to unregister the altmode, blocking
> on the altmode driver's cancel_work_sync call.
>
> Because the state check isn't protected, there is a small window
> where the Alt Mode driver could determine that the TCPM is
> in a ready state and attempt to grab the lock while the
> TCPM grabs the lock and changes the TCPM state to one that
> causes the deadlock.
>
> Change tcpm_queue_vdm_unlocked to queue for tcpm_queue_vdm_work,
> which can perform the state check while holding the TCPM lock
> while the Alt Mode lock is no longer held. This requires a new
> struct to hold the vdm data, altmode_vdm_event.
>
> Fixes: cdc9946ea637 ("usb: typec: tcpm: enforce ready state when queueing alt mode vdm")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: RD Babiera <rdbabiera@xxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> drivers/usb/typec/tcpm/tcpm.c | 91 +++++++++++++++++++++++++++--------
> 1 file changed, 71 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 784fa23102f9..9b8d98328ddb 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -597,6 +597,15 @@ struct pd_rx_event {
> enum tcpm_transmit_type rx_sop_type;
> };
>
> +struct altmode_vdm_event {
> + struct kthread_work work;
> + struct tcpm_port *port;
> + u32 header;
> + u32 *data;
> + int cnt;
> + enum tcpm_transmit_type tx_sop_type;
> +};
> +
> static const char * const pd_rev[] = {
> [PD_REV10] = "rev1",
> [PD_REV20] = "rev2",
> @@ -1610,18 +1619,68 @@ static void tcpm_queue_vdm(struct tcpm_port *port, const u32 header,
> mod_vdm_delayed_work(port, 0);
> }
>
> -static void tcpm_queue_vdm_unlocked(struct tcpm_port *port, const u32 header,
> - const u32 *data, int cnt, enum tcpm_transmit_type tx_sop_type)
> +static void tcpm_queue_vdm_work(struct kthread_work *work)
> {
> - if (port->state != SRC_READY && port->state != SNK_READY &&
> - port->state != SRC_VDM_IDENTITY_REQUEST)
> - return;
> + struct altmode_vdm_event *event = container_of(work,
> + struct altmode_vdm_event,
> + work);
> + struct tcpm_port *port = event->port;
>
> mutex_lock(&port->lock);
> - tcpm_queue_vdm(port, header, data, cnt, tx_sop_type);
> + if (port->state != SRC_READY && port->state != SNK_READY &&
> + port->state != SRC_VDM_IDENTITY_REQUEST) {
> + tcpm_log_force(port, "dropping altmode_vdm_event");
> + goto port_unlock;
> + }
> +
> + tcpm_queue_vdm(port, event->header, event->data, event->cnt, event->tx_sop_type);
> +
> +port_unlock:
> + kfree(event->data);
> + kfree(event);
> mutex_unlock(&port->lock);
> }
>
> +static int tcpm_queue_vdm_unlocked(struct tcpm_port *port, const u32 header,
> + const u32 *data, int cnt, enum tcpm_transmit_type tx_sop_type)
> +{
> + struct altmode_vdm_event *event;
> + u32 *data_cpy;
> + int ret = -ENOMEM;
> +
> + event = kzalloc(sizeof(*event), GFP_KERNEL);
> + if (!event)
> + goto err_event;
> +
> + data_cpy = kcalloc(cnt, sizeof(u32), GFP_KERNEL);
> + if (!data_cpy)
> + goto err_data;
> +
> + kthread_init_work(&event->work, tcpm_queue_vdm_work);
> + event->port = port;
> + event->header = header;
> + memcpy(data_cpy, data, sizeof(u32) * cnt);
> + event->data = data_cpy;
> + event->cnt = cnt;
> + event->tx_sop_type = tx_sop_type;
> +
> + ret = kthread_queue_work(port->wq, &event->work);
> + if (!ret) {
> + ret = -EBUSY;
> + goto err_queue;
> + }
> +
> + return 0;
> +
> +err_queue:
> + kfree(data_cpy);
> +err_data:
> + kfree(event);
> +err_event:
> + tcpm_log_force(port, "failed to queue altmode vdm, err:%d", ret);
> + return ret;
> +}
> +
> static void svdm_consume_identity(struct tcpm_port *port, const u32 *p, int cnt)
> {
> u32 vdo = p[VDO_INDEX_IDH];
> @@ -2832,8 +2891,7 @@ static int tcpm_altmode_enter(struct typec_altmode *altmode, u32 *vdo)
> header = VDO(altmode->svid, vdo ? 2 : 1, svdm_version, CMD_ENTER_MODE);
> header |= VDO_OPOS(altmode->mode);
>
> - tcpm_queue_vdm_unlocked(port, header, vdo, vdo ? 1 : 0, TCPC_TX_SOP);
> - return 0;
> + return tcpm_queue_vdm_unlocked(port, header, vdo, vdo ? 1 : 0, TCPC_TX_SOP);
> }
>
> static int tcpm_altmode_exit(struct typec_altmode *altmode)
> @@ -2849,8 +2907,7 @@ static int tcpm_altmode_exit(struct typec_altmode *altmode)
> header = VDO(altmode->svid, 1, svdm_version, CMD_EXIT_MODE);
> header |= VDO_OPOS(altmode->mode);
>
> - tcpm_queue_vdm_unlocked(port, header, NULL, 0, TCPC_TX_SOP);
> - return 0;
> + return tcpm_queue_vdm_unlocked(port, header, NULL, 0, TCPC_TX_SOP);
> }
>
> static int tcpm_altmode_vdm(struct typec_altmode *altmode,
> @@ -2858,9 +2915,7 @@ static int tcpm_altmode_vdm(struct typec_altmode *altmode,
> {
> struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
>
> - tcpm_queue_vdm_unlocked(port, header, data, count - 1, TCPC_TX_SOP);
> -
> - return 0;
> + return tcpm_queue_vdm_unlocked(port, header, data, count - 1, TCPC_TX_SOP);
> }
>
> static const struct typec_altmode_ops tcpm_altmode_ops = {
> @@ -2884,8 +2939,7 @@ static int tcpm_cable_altmode_enter(struct typec_altmode *altmode, enum typec_pl
> header = VDO(altmode->svid, vdo ? 2 : 1, svdm_version, CMD_ENTER_MODE);
> header |= VDO_OPOS(altmode->mode);
>
> - tcpm_queue_vdm_unlocked(port, header, vdo, vdo ? 1 : 0, TCPC_TX_SOP_PRIME);
> - return 0;
> + return tcpm_queue_vdm_unlocked(port, header, vdo, vdo ? 1 : 0, TCPC_TX_SOP_PRIME);
> }
>
> static int tcpm_cable_altmode_exit(struct typec_altmode *altmode, enum typec_plug_index sop)
> @@ -2901,8 +2955,7 @@ static int tcpm_cable_altmode_exit(struct typec_altmode *altmode, enum typec_plu
> header = VDO(altmode->svid, 1, svdm_version, CMD_EXIT_MODE);
> header |= VDO_OPOS(altmode->mode);
>
> - tcpm_queue_vdm_unlocked(port, header, NULL, 0, TCPC_TX_SOP_PRIME);
> - return 0;
> + return tcpm_queue_vdm_unlocked(port, header, NULL, 0, TCPC_TX_SOP_PRIME);
> }
>
> static int tcpm_cable_altmode_vdm(struct typec_altmode *altmode, enum typec_plug_index sop,
> @@ -2910,9 +2963,7 @@ static int tcpm_cable_altmode_vdm(struct typec_altmode *altmode, enum typec_plug
> {
> struct tcpm_port *port = typec_altmode_get_drvdata(altmode);
>
> - tcpm_queue_vdm_unlocked(port, header, data, count - 1, TCPC_TX_SOP_PRIME);
> -
> - return 0;
> + return tcpm_queue_vdm_unlocked(port, header, data, count - 1, TCPC_TX_SOP_PRIME);
> }
>
> static const struct typec_cable_ops tcpm_cable_ops = {
>
> base-commit: 615dca38c2eae55aff80050275931c87a812b48c
> --
> 2.49.0.967.g6a0df3ecc3-goog
--
heikki
