[Patch v4] usb: core: stop USB enumeration if too many retries

From: Ray Chi
Date: Tue Sep 27 2022 - 12:27:28 EST

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When a broken USB accessory connects to a USB host, usbcore might
keep doing enumeration retries. If the host has a watchdog mechanism,
the kernel panic will happen on the host.

This patch provides an attribute early_stop to limit the numbers of retries
for each port of a hub. If a port was marked with early_stop attribute,
unsuccessful connection attempts will fail quickly. In addition, if an
early_stop port has failed to initialize, it will ignore all future
connection events until early_stop attribute is clear.

Signed-off-by: Ray Chi <raychi@xxxxxxxxxx>
---
Changes since v3:
- rename the attribute from quick_init to early_stop
- rename the variable of port_dev from ignore_connect to ignore_event
- modify changelog, documentation
- add more comments for hub_port_stop_enumerate()

Changes since v2:
- replace the quirk with the attribute
- Document the attribute
- modify hub_port_stop_enumerate() position in port_event()
- modify the changelog

Changes since v1:
- remove usb_hub_set_port_power()
- add a variable ignore_connect into struct port_dev
- modify hub_port_stop_enumerate() and set ignore_connect in
this function
- avoid calling hub_port_connect_change() in port_event()
---
Documentation/ABI/testing/sysfs-bus-usb | 11 +++++
drivers/usb/core/hub.c | 59 +++++++++++++++++++++++++
drivers/usb/core/hub.h | 4 ++
drivers/usb/core/port.c | 27 +++++++++++
4 files changed, 101 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 568103d3376e..545c2dd97ed0 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -264,6 +264,17 @@ Description:
attached to the port will not be detected, initialized,
or enumerated.

+What: /sys/bus/usb/devices/.../<hub_interface>/port<X>/early_stop
+Date: Sep 2022
+Contact: Ray Chi <raychi@xxxxxxxxxx>
+Description:
+ Some USB hosts have some watchdog mechanisms so that the device
+ may enter ramdump if it takes a long time during port initialization.
+ This attribute allows each port just has two attempts so that the
+ port initialization will be failed quickly. In addition, if a port
+ which is marked with early_stop has failed to initialize, it will ignore
+ all future connections until this attribute is clear.
+
What: /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index bbab424b0d55..5510dbef3243 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3081,6 +3081,48 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
return status;
}

+/*
+ * hub_port_stop_enumerate - stop USB enumeration or ignore port events
+ * @hub: target hub
+ * @port1: port num of the port
+ * @retries: port retries number of hub_port_init()
+ *
+ * Return:
+ * true: ignore port actions/events or give up connection attempts.
+ * false: keep original behavior.
+ *
+ * This function will be based on retries to check whether the port which is
+ * marked with early_stop attribute would stop enumeration or ignore events.
+ *
+ * Note:
+ * This function didn't change anything if early_stop is not set, and it will
+ * prevent all connection attempts when early_stop is set and the attempts of
+ * the port are more than 1.
+ */
+static bool hub_port_stop_enumerate(struct usb_hub *hub, int port1, int retries)
+{
+ struct usb_port *port_dev = hub->ports[port1 - 1];
+
+ if (port_dev->early_stop) {
+ if (port_dev->ignore_event)
+ return true;
+
+ /*
+ * We want unsuccessful attempts to fail quickly.
+ * Since some devices may need one failure during
+ * port initialization, we allow two tries but no
+ * more.
+ */
+ if (retries < 1)
+ return false;
+
+ port_dev->ignore_event = 1;
+ } else
+ port_dev->ignore_event = 0;
+
+ return port_dev->ignore_event;
+}
+
/* Check if a port is power on */
int usb_port_is_power_on(struct usb_hub *hub, unsigned int portstatus)
{
@@ -4855,6 +4897,11 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
buf->bMaxPacketSize0;
kfree(buf);

+ if (r < 0 && hub_port_stop_enumerate(hub, port1, retries)) {
+ retval = r;
+ goto fail;
+ }
+
retval = hub_port_reset(hub, port1, udev, delay, false);
if (retval < 0) /* error or disconnect */
goto fail;
@@ -5387,6 +5434,9 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
if ((status == -ENOTCONN) || (status == -ENOTSUPP))
break;

+ if (hub_port_stop_enumerate(hub, port1, i))
+ break;
+
/* When halfway through our retry count, power-cycle the port */
if (i == (PORT_INIT_TRIES - 1) / 2) {
dev_info(&port_dev->dev, "attempt power cycle\n");
@@ -5614,6 +5664,10 @@ static void port_event(struct usb_hub *hub, int port1)
if (!pm_runtime_active(&port_dev->dev))
return;

+ /* skip port actions if ignore_event is true*/
+ if (hub_port_stop_enumerate(hub, port1, 0))
+ return;
+
if (hub_handle_remote_wakeup(hub, port1, portstatus, portchange))
connect_change = 1;

@@ -5934,6 +5988,9 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
ret = hub_port_init(parent_hub, udev, port1, i);
if (ret >= 0 || ret == -ENOTCONN || ret == -ENODEV)
break;
+
+ if (hub_port_stop_enumerate(parent_hub, port1, i))
+ goto stop_enumerate;
}
mutex_unlock(hcd->address0_mutex);

@@ -6022,6 +6079,8 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
udev->bos = bos;
return 0;

+stop_enumerate:
+ mutex_unlock(hcd->address0_mutex);
re_enumerate:
usb_release_bos_descriptor(udev);
udev->bos = bos;
diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index b2925856b4cb..e23833562e4f 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -90,6 +90,8 @@ struct usb_hub {
* @is_superspeed cache super-speed status
* @usb3_lpm_u1_permit: whether USB3 U1 LPM is permitted.
* @usb3_lpm_u2_permit: whether USB3 U2 LPM is permitted.
+ * @early_stop: whether port initialization will be stopped earlier.
+ * @ignore_event: whether events of the port are ignored.
*/
struct usb_port {
struct usb_device *child;
@@ -103,6 +105,8 @@ struct usb_port {
u32 over_current_count;
u8 portnum;
u32 quirks;
+ unsigned int early_stop:1;
+ unsigned int ignore_event:1;
unsigned int is_superspeed:1;
unsigned int usb3_lpm_u1_permit:1;
unsigned int usb3_lpm_u2_permit:1;
diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 38c1a4f4fdea..126da9408359 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -17,6 +17,32 @@ static int usb_port_block_power_off;

static const struct attribute_group *port_dev_group[];

+static ssize_t early_stop_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct usb_port *port_dev = to_usb_port(dev);
+
+ return sysfs_emit(buf, "%s\n", port_dev->early_stop ? "yes" : "no");
+}
+
+static ssize_t early_stop_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct usb_port *port_dev = to_usb_port(dev);
+ bool value;
+
+ if (kstrtobool(buf, &value))
+ return -EINVAL;
+
+ if (value)
+ port_dev->early_stop = 1;
+ else
+ port_dev->early_stop = 0;
+
+ return count;
+}
+static DEVICE_ATTR_RW(early_stop);
+
static ssize_t disable_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -236,6 +262,7 @@ static struct attribute *port_dev_attrs[] = {
&dev_attr_quirks.attr,
&dev_attr_over_current_count.attr,
&dev_attr_disable.attr,
+ &dev_attr_early_stop.attr,
NULL,
};

--
2.37.3.998.g577e59143f-goog

Next message: Chih-En Lin: "[RFC PATCH v2 0/9] Introduce Copy-On-Write to Page Table"
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