5.4-stable review patch. If anyone has any objections, please let me know.
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From: Elson Roy Serrao quic_eserrao@quicinc.com
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@kernel.org Signed-off-by: Elson Roy Serrao quic_eserrao@quicinc.com Reviewed-by: Heikki Krogerus heikki.krogerus@linux.intel.com Link: https://lore.kernel.org/r/20250206193950.22421-1-quic_eserrao@quicinc.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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;