On Sat, Feb 8, 2020 at 7:43 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > When bpf_prog is removed from kallsyms it's on the way > out to be removed, so we don't care about lnode state. > > However the bpf_ksym_del will be used also by bpf_trampoline > and bpf_dispatcher objects, which stay allocated even when > they are not in kallsyms list, hence the lnode re-init. > > The list_del_rcu commentary states that we need to call > synchronize_rcu, before we can change/re-init the list_head > pointers. > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > --- Wouldn't it make more sense to have patches 7 though 10 as a one patch? It's a generalization of ksym from being bpf_prog-specific to be more general (which this initialization fix is part of, arguably). > kernel/bpf/core.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > index 73242fd07893..66b17bea286e 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -676,6 +676,13 @@ void bpf_ksym_del(struct bpf_ksym *ksym) > spin_lock_bh(&bpf_lock); > __bpf_ksym_del(ksym); > spin_unlock_bh(&bpf_lock); > + > + /* > + * As explained in list_del_rcu, We must call synchronize_rcu > + * before changing list_head pointers. > + */ > + synchronize_rcu(); > + INIT_LIST_HEAD_RCU(&ksym->lnode); > } > > static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp) > -- > 2.24.1 >
