[Patch v3] usb: core: stop USB enumeration if too many retries

Ray Chi
2022-09-08T10:41:07Z

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.

The patch provide a attribute to limit the numbers of retries and
timeout lengths. In addition, it also adds a function to stop the
port initialization and ignore events on the port if the broken
accessory is still connected.

Signed-off-by: Ray Chi <raychi@google.com>
---
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 | 9 ++++++
drivers/usb/core/hub.c | 39 +++++++++++++++++++++++++
drivers/usb/core/hub.h | 4 +++
drivers/usb/core/port.c | 23 +++++++++++++++
4 files changed, 75 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 568103d3376e..d44c8aaef929 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -264,6 +264,15 @@ Description:
attached to the port will not be detected, initialized,
or enumerated.

+What: /sys/bus/usb/devices/.../<hub_interface>/port<X>/quick_init
+Date: Sep 2022
+Contact: Ray Chi <raychi@google.com>
+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 limits the numbers of retries and timeout lengths once
+ an initialization of the port meets failures.
+
What: /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index d4b1e70d1498..f22caa133274 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3081,6 +3081,29 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
return status;
}

+/* Check whether a hub would stop enumeration or ignore events on the port. */
+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->quick_init) {
+ if (port_dev->ignore_connect)
+ return true;
+
+ /*
+ * Since some normal devices will be timeout in the first attempt,
+ * set the condition to half of the retries
+ */
+ if (retries < (PORT_INIT_TRIES - 1) / 2)
+ return false;
+
+ port_dev->ignore_connect = true;
+ } else
+ port_dev->ignore_connect = false;
+
+ return port_dev->ignore_connect;
+}
+
/* Check if a port is power on */
int usb_port_is_power_on(struct usb_hub *hub, unsigned int portstatus)
{
@@ -4855,6 +4878,11 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
buf->bMaxPacketSize0;
kfree(buf);

+ if (r < 0 && port_dev->quick_init) {
+ retval = r;
+ goto fail;
+ }
+
retval = hub_port_reset(hub, port1, udev, delay, false);
if (retval < 0) /* error or disconnect */
goto fail;
@@ -5387,6 +5415,9 @@ 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 +5645,9 @@ static void port_event(struct usb_hub *hub, int port1)
if (!pm_runtime_active(&port_dev->dev))
return;

+ if (hub_port_stop_enumerate(hub, port1, 0))
+ return;
+
if (hub_handle_remote_wakeup(hub, port1, portstatus, portchange))
connect_change = 1;

@@ -5934,6 +5968,9 @@ 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 +6059,8 @@ 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..57995ec3af58 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.
+ * @ignore_connect: ignore the connection or not.
+ * @quick_init: limit the numbers of retries for port initialization
*/
struct usb_port {
struct usb_device *child;
@@ -103,6 +105,8 @@ struct usb_port {
u32 over_current_count;
u8 portnum;
u32 quirks;
+ bool ignore_connect;
+ bool quick_init;
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..7d5acd3ff353 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -17,6 +17,28 @@ static int usb_port_block_power_off;

static const struct attribute_group *port_dev_group[];

+static ssize_t quick_init_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->quick_init ? "yes" : "no");
+}
+
+static ssize_t quick_init_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;
+
+ port_dev->quick_init = value;
+ return count;
+}
+static DEVICE_ATTR_RW(quick_init);
+
static ssize_t disable_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -236,6 +258,7 @@ static struct attribute *port_dev_attrs[] = {
&dev_attr_quirks.attr,
&dev_attr_over_current_count.attr,
&dev_attr_disable.attr,
+ &dev_attr_quick_init.attr,
NULL,
};

--
2.37.2.789.g6183377224-goog