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

bpf: Mark tracing_multi trampolines as ftrace managed

Since tracing_multi link does not set ftrace_managed, it would fail to
release the tracing_multi link when attaching tracing_multi link and
then attaching fentry link.

[ 3.714215] WARNING: kernel/bpf/trampoline.c:1727 at bpf_trampoline_multi_detach+0x20b/0x240, CPU#1: test_progs/97
...
[ 3.733170] bpf_tracing_multi_link_release+0x14/0x30
[ 3.733890] bpf_link_free+0x58/0x130
[ 3.734414] bpf_link_release+0x23/0x30

Fix it by setting 'ftrace_managed = true' in register_fentry_multi().