net/sched: act_api: avoid dereferencing ERR_PTR in tcf_idrinfo_destroy

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

net/sched: act_api: avoid dereferencing ERR_PTR in tcf_idrinfo_destroy

syzbot reported a crash in tc_act_in_hw() during netns teardown where tcf_idrinfo_destroy() passed an ERR_PTR(-EBUSY) value as a tc_action pointer, leading to an invalid dereference.

Guard against ERR_PTR entries when iterating the action IDR so teardown does not call tc_act_in_hw() on an error pointer.