linux-kernel - Re: [PATCH bpf-next v2 7/8] bpf: Add tests for task_local

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Message-ID: <CACYkzJ7v4TNopZ0VhFezax-i3TF59Ok2mfgb_W+mTH52fd_gRw@mail.gmail.com>
Date:   Wed, 4 Nov 2020 12:03:41 +0100
From:   KP Singh <kpsingh@...omium.org>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Paul Turner <pjt@...gle.com>,
        Jann Horn <jannh@...gle.com>, Hao Luo <haoluo@...gle.com>
Subject: Re: [PATCH bpf-next v2 7/8] bpf: Add tests for task_local_storage

[...]

> > Ahh. Yes. That should do it. Right now I don't see concerns with safety
> > of the bpf_spin_lock in bpf_lsm progs.
>
> What about sleepable lsm hooks? Normally we wouldn't expect to sleep with
> a spinlock held. Should we have a check to ensure programs bpf_spin_lock
> are not also sleepable?

Thanks. Yes, I added that to my patch:

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 61f8cc52fd5b..93383df2140b 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -63,6 +63,10 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const
struct bpf_prog *prog)
                return &bpf_task_storage_get_proto;
        case BPF_FUNC_task_storage_delete:
                return &bpf_task_storage_delete_proto;
+       case BPF_FUNC_spin_lock:
+               return &bpf_spin_lock_proto;
+       case BPF_FUNC_spin_unlock:
+               return &bpf_spin_unlock_proto;
        default:
                return tracing_prog_func_proto(func_id, prog);
        }
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 314018e8fc12..8892f7ba2041 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9739,6 +9739,23 @@ static int check_map_prog_compatibility(struct
bpf_verifier_env *env,
                return -EINVAL;
        }

+       if (map_value_has_spin_lock(map)) {
+               if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
+                       verbose(env, "socket filter progs cannot use
bpf_spin_lock yet\n");
+                       return -EINVAL;
+               }
+
+               if (is_tracing_prog_type(prog_type)) {
+                       verbose(env, "tracing progs cannot use
bpf_spin_lock yet\n");
+                       return -EINVAL;
+               }
+
+               if (prog->aux->sleepable) {
+                       verbose(env, "sleepable progs cannot use
bpf_spin_lock\n");
+                       return -EINVAL;
+               }
+       }
+