CVE-2024-35986: Use After Free

In the Linux kernel, the following vulnerability has been resolved:

phy: ti: tusb1210: Resolve charger-det crash if charger psy is unregistered

The power_supply frame-work is not really designed for there to be long living in kernel references to power_supply devices.

Specifically unregistering a power_supply while some other code has a reference to it triggers a WARN in power_supply_unregister():

WARN_ON(atomic_dec_return(&psy->use_cnt));

Folllowed by the power_supply still getting removed and the backing data freed anyway, leaving the tusb1210 charger-detect code with a dangling reference, resulting in a crash the next time tusb1210_get_online() is called.

Fix this by only holding the reference in tusb1210_get_online() freeing it at the end of the function. Note this still leaves a theoretical race window, but it avoids the issue when manually rmmod-ing the charger chip driver during development.