CVE-2026-74740

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

net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain

tcf_action_exec() handles TC_ACT_GOTO_CHAIN by first checking

rcu_access_pointer(a->goto_chain) and then calling

tcf_action_goto_chain_exec(), which does a second, independent

rcu_dereference_bh(a->goto_chain) read and immediately dereferences

chain->filter_chain. A concurrent tcf_action_set_ctrlact() (e.g. the gact

replace path) can clear a->goto_chain between the two reads, so the second

read returns NULL and tcf_action_goto_chain_exec() dereferences NULL.

Fix the race by doing a single rcu_dereference_bh() read of a->goto_chain

in tcf_action_exec(), checking it once for NULL, and passing the resulting

chain pointer into tcf_action_goto_chain_exec(). This turns the split

check/use into a single check/use on one value.