On Thu, Jul 28, 2022 at 07:40:48AM -0400, Xu Kuohai wrote: > From: Xu Kuohai <xukuohai@xxxxxxxxxx> SNIP > > It's caused by a NULL tr->fops passed to ftrace_set_filter_ip(). tr->fops > is initialized to NULL and is assigned to an allocated memory address if > CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS is enabled. Since there is no > direct call on arm64 yet, the config can't be enabled. > > To fix it, call ftrace_set_filter_ip() only if tr->fops is not NULL. > > Fixes: 00963a2e75a8 ("bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)") > Reported-by: Bruno Goncalves <bgoncalv@xxxxxxxxxx> > Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx> > Tested-by: Bruno Goncalves <bgoncalv@xxxxxxxxxx> > Acked-by: Song Liu <songliubraving@xxxxxx> > --- > kernel/bpf/trampoline.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c > index 42e387a12694..0d5a9e0b9a7b 100644 > --- a/kernel/bpf/trampoline.c > +++ b/kernel/bpf/trampoline.c > @@ -255,8 +255,15 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr) > return -ENOENT; > > if (tr->func.ftrace_managed) { > - ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 0); > - ret = register_ftrace_direct_multi(tr->fops, (long)new_addr); > + if (tr->fops) > + ret = ftrace_set_filter_ip(tr->fops, (unsigned long)ip, > + 0, 0); > + else > + ret = -ENOTSUPP; > + > + if (!ret) > + ret = register_ftrace_direct_multi(tr->fops, > + (long)new_addr); > } else { > ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr); > } do we need to do the same also in unregister_fentry and modify_fentry ? jirka