On Tue, Apr 13, 2021 at 03:03:27PM -0700, Andrii Nakryiko wrote:
> On Mon, Apr 12, 2021 at 9:28 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > Currently we don't allow re-attaching of trampolines. Once
> > it's detached, it can't be re-attach even when the program
> > is still loaded.
> >
> > Adding the possibility to re-attach the loaded tracing and
> > lsm programs.
> >
> > Fixing missing unlock with proper cleanup goto jump reported
> > by Julia.
> >
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Reported-by: Julia Lawall <julia.lawall@xxxxxxx>
> > Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> > kernel/bpf/syscall.c | 23 +++++++++++++++++------
> > kernel/bpf/trampoline.c | 2 +-
> > 2 files changed, 18 insertions(+), 7 deletions(-)
> >
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 6428634da57e..f02c6a871b4f 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -2645,14 +2645,25 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
> > * target_btf_id using the link_create API.
> > *
> > * - if tgt_prog == NULL when this function was called using the old
> > - * raw_tracepoint_open API, and we need a target from prog->aux
> > - *
> > - * The combination of no saved target in prog->aux, and no target
> > - * specified on load is illegal, and we reject that here.
> > + * raw_tracepoint_open API, and we need a target from prog->aux
> > + *
> > + * - if prog->aux->dst_trampoline and tgt_prog is NULL, the program
> > + * was detached and is going for re-attachment.
> > */
> > if (!prog->aux->dst_trampoline && !tgt_prog) {
> > - err = -ENOENT;
> > - goto out_unlock;
> > + /*
> > + * Allow re-attach for TRACING and LSM programs. If it's
> > + * currently linked, bpf_trampoline_link_prog will fail.
> > + * EXT programs need to specify tgt_prog_fd, so they
> > + * re-attach in separate code path.
> > + */
> > + if (prog->type != BPF_PROG_TYPE_TRACING &&
> > + prog->type != BPF_PROG_TYPE_LSM) {
> > + err = -EINVAL;
> > + goto out_unlock;
> > + }
> > + btf_id = prog->aux->attach_btf_id;
> > + key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, btf_id);
> > }
> >
> > if (!prog->aux->dst_trampoline ||
> > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> > index 1f3a4be4b175..48b8b9916aa2 100644
> > --- a/kernel/bpf/trampoline.c
> > +++ b/kernel/bpf/trampoline.c
> > @@ -437,7 +437,7 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
> > tr->extension_prog = NULL;
> > goto out;
> > }
> > - hlist_del(&prog->aux->tramp_hlist);
> > + hlist_del_init(&prog->aux->tramp_hlist);
>
> there is another hlist_del few lines above in error handling path of
> bpf_trampoline_link_prog(), it should probably be also updated to
> hlist_del_init(), no?
ugh, that one is missing.. will fix
thanks,
jirka
>
> > tr->progs_cnt[kind]--;
> > err = bpf_trampoline_update(tr);
> > out:
> > --
> > 2.30.2
> >
>
