diff mbox series

[v2] usb: typec: tcpm: move tcpm_queue_vdm_unlocked to asynchronous work

Message ID 20250506232853.1968304-2-rdbabiera@google.com
State New
Headers show
Series [v2] usb: typec: tcpm: move tcpm_queue_vdm_unlocked to asynchronous work | expand

Commit Message

RD Babiera May 6, 2025, 11:28 p.m. UTC 
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. The callstack is provided below:

[110121.667392][    C7] Call trace:
[110121.667396][    C7]  __switch_to+0x174/0x338
[110121.667406][    C7]  __schedule+0x608/0x9f0
[110121.667414][    C7]  schedule+0x7c/0xe8
[110121.667423][    C7]  kernfs_drain+0xb0/0x114
[110121.667431][    C7]  __kernfs_remove+0x16c/0x20c
[110121.667436][    C7]  kernfs_remove_by_name_ns+0x74/0xe8
[110121.667442][    C7]  sysfs_remove_group+0x84/0xe8
[110121.667450][    C7]  sysfs_remove_groups+0x34/0x58
[110121.667458][    C7]  device_remove_groups+0x10/0x20
[110121.667464][    C7]  device_release_driver_internal+0x164/0x2e4
[110121.667475][    C7]  device_release_driver+0x18/0x28
[110121.667484][    C7]  bus_remove_device+0xec/0x118
[110121.667491][    C7]  device_del+0x1e8/0x4ac
[110121.667498][    C7]  device_unregister+0x18/0x38
[110121.667504][    C7]  typec_unregister_altmode+0x30/0x44
[110121.667515][    C7]  tcpm_reset_port+0xac/0x370
[110121.667523][    C7]  tcpm_snk_detach+0x84/0xb8
[110121.667529][    C7]  run_state_machine+0x4c0/0x1b68
[110121.667536][    C7]  tcpm_state_machine_work+0x94/0xe4
[110121.667544][    C7]  kthread_worker_fn+0x10c/0x244
[110121.667552][    C7]  kthread+0x104/0x1d4
[110121.667557][    C7]  ret_from_fork+0x10/0x20

[110121.667689][    C7] Workqueue: events dp_altmode_work
[110121.667697][    C7] Call trace:
[110121.667701][    C7]  __switch_to+0x174/0x338
[110121.667710][    C7]  __schedule+0x608/0x9f0
[110121.667717][    C7]  schedule+0x7c/0xe8
[110121.667725][    C7]  schedule_preempt_disabled+0x24/0x40
[110121.667733][    C7]  __mutex_lock+0x408/0xdac
[110121.667741][    C7]  __mutex_lock_slowpath+0x14/0x24
[110121.667748][    C7]  mutex_lock+0x40/0xec
[110121.667757][    C7]  tcpm_altmode_enter+0x78/0xb4
[110121.667764][    C7]  typec_altmode_enter+0xdc/0x10c
[110121.667769][    C7]  dp_altmode_work+0x68/0x164
[110121.667775][    C7]  process_one_work+0x1e4/0x43c
[110121.667783][    C7]  worker_thread+0x25c/0x430
[110121.667789][    C7]  kthread+0x104/0x1d4
[110121.667794][    C7]  ret_from_fork+0x10/0x20

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>
---
Changes from v1:
* modified commit message to include call stack
---
 drivers/usb/typec/tcpm/tcpm.c | 91 +++++++++++++++++++++++++++--------
 1 file changed, 71 insertions(+), 20 deletions(-)


base-commit: 588d032e9e566997db3213dee145dbe3bda297b6

Comments

Badhri Jagan Sridharan May 7, 2025, 1:13 a.m. UTC | #1 
On Tue, May 6, 2025 at 4:29 PM RD Babiera <rdbabiera@google.com> 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. The callstack is provided below:
>
> [110121.667392][    C7] Call trace:
> [110121.667396][    C7]  __switch_to+0x174/0x338
> [110121.667406][    C7]  __schedule+0x608/0x9f0
> [110121.667414][    C7]  schedule+0x7c/0xe8
> [110121.667423][    C7]  kernfs_drain+0xb0/0x114
> [110121.667431][    C7]  __kernfs_remove+0x16c/0x20c
> [110121.667436][    C7]  kernfs_remove_by_name_ns+0x74/0xe8
> [110121.667442][    C7]  sysfs_remove_group+0x84/0xe8
> [110121.667450][    C7]  sysfs_remove_groups+0x34/0x58
> [110121.667458][    C7]  device_remove_groups+0x10/0x20
> [110121.667464][    C7]  device_release_driver_internal+0x164/0x2e4
> [110121.667475][    C7]  device_release_driver+0x18/0x28
> [110121.667484][    C7]  bus_remove_device+0xec/0x118
> [110121.667491][    C7]  device_del+0x1e8/0x4ac
> [110121.667498][    C7]  device_unregister+0x18/0x38
> [110121.667504][    C7]  typec_unregister_altmode+0x30/0x44
> [110121.667515][    C7]  tcpm_reset_port+0xac/0x370
> [110121.667523][    C7]  tcpm_snk_detach+0x84/0xb8
> [110121.667529][    C7]  run_state_machine+0x4c0/0x1b68
> [110121.667536][    C7]  tcpm_state_machine_work+0x94/0xe4
> [110121.667544][    C7]  kthread_worker_fn+0x10c/0x244
> [110121.667552][    C7]  kthread+0x104/0x1d4
> [110121.667557][    C7]  ret_from_fork+0x10/0x20
>
> [110121.667689][    C7] Workqueue: events dp_altmode_work
> [110121.667697][    C7] Call trace:
> [110121.667701][    C7]  __switch_to+0x174/0x338
> [110121.667710][    C7]  __schedule+0x608/0x9f0
> [110121.667717][    C7]  schedule+0x7c/0xe8
> [110121.667725][    C7]  schedule_preempt_disabled+0x24/0x40
> [110121.667733][    C7]  __mutex_lock+0x408/0xdac
> [110121.667741][    C7]  __mutex_lock_slowpath+0x14/0x24
> [110121.667748][    C7]  mutex_lock+0x40/0xec
> [110121.667757][    C7]  tcpm_altmode_enter+0x78/0xb4
> [110121.667764][    C7]  typec_altmode_enter+0xdc/0x10c
> [110121.667769][    C7]  dp_altmode_work+0x68/0x164
> [110121.667775][    C7]  process_one_work+0x1e4/0x43c
> [110121.667783][    C7]  worker_thread+0x25c/0x430
> [110121.667789][    C7]  kthread+0x104/0x1d4
> [110121.667794][    C7]  ret_from_fork+0x10/0x20
>
> 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>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>

> ---
> Changes from v1:
> * modified commit message to include call stack
> ---
>  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: 588d032e9e566997db3213dee145dbe3bda297b6
> --
> 2.49.0.967.g6a0df3ecc3-goog
>
diff mbox series

Patch

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 = {