From: Elson Roy Serrao <quic_eserrao@xxxxxxxxxxx>
commit 634775a752a86784511018a108f3b530cc3399a7 upstream.
The role switch registration and set_role() can happen in parallel as they
are invoked independent of each other. There is a possibility that a driver
might spend significant amount of time in usb_role_switch_register() API
due to the presence of time intensive operations like component_add()
which operate under common mutex. This leads to a time window after
allocating the switch and before setting the registered flag where the set
role notifications are dropped. Below timeline summarizes this behavior
Thread1 | Thread2
usb_role_switch_register() |
| |
---> allocate switch |
| |
---> component_add() | usb_role_switch_set_role()
| | |
| | --> Drop role notifications
| | since sw->registered
| | flag is not set.
| |
--->Set registered flag.|
To avoid this, set the registered flag early on in the switch register
API.
Fixes: b787a3e78175 ("usb: roles: don't get/set_role() when usb_role_switch is unregistered")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Elson Roy Serrao <quic_eserrao@xxxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250206193950.22421-1-quic_eserrao@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/roles/class.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -317,14 +317,15 @@ usb_role_switch_register(struct device *
sw->dev.type = &usb_role_dev_type;
dev_set_name(&sw->dev, "%s-role-switch", dev_name(parent));
+ sw->registered = true;
+
ret = device_register(&sw->dev);
if (ret) {
+ sw->registered = false;
put_device(&sw->dev);
return ERR_PTR(ret);
}
- sw->registered = true;
-
/* TODO: Symlinks for the host port and the device controller. */
return sw;
Patches currently in stable-queue which might be from quic_eserrao@xxxxxxxxxxx are
queue-5.4/usb-roles-set-switch-registered-flag-early-on.patch
