Re: [PATCH v1] usb: typec: tcpm: move tcpm_queue_vdm_unlocked to asynchronous work

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@vger.kernel.org Signed-off-by: RD Babiera rdbabiera@google.com

Reviewed-by: Heikki Krogerus heikki.krogerus@linux.intel.com

---

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