In the Linux kernel, the following vulnerability has been resolved:
OPP: Fix race between OPP addition and lookup
A race exists between dev_pm_opp_add_dynamic() and
dev_pm_opp_find_freq_exact():
CPU0 (add) CPU1 (lookup)
——————————- ——————————
_opp_add()
mutex_lock()
list_add(&new_opp->node, head)
mutex_unlock() _opp_table_find_key()
mutex_lock()
dev_pm_opp_get(opp)
kref_get()
mutex_unlock()
kref_init(&new_opp->kref)
dev_pm_opp_put()
kref_put_mutex()
The newly added OPP is inserted into the list before its kref is
initialized. A concurrent lookup can find this OPP and increment its
reference count while it is still uninitialized, leading to refcount
corruption and a potential premature free.
Fix this by initializing ->kref and ->opp_table before making the OPP
visible via list_add(). This ensures any concurrent lookup observes a
fully initialized object.
[ Viresh: Updated commit log ]
