| Message ID | 20201104164453.74390-6-kpsingh@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next,v3,1/9] bpf: Implement task local storage | expand |
On Wed, Nov 04, 2020 at 05:44:49PM +0100, KP Singh wrote: > From: KP Singh <kpsingh@google.com> > > Usage of spin locks was not allowed for tracing programs due to > insufficient preemption checks. The verifier does not currently prevent > LSM programs from using spin locks, but the helpers are not exposed > via bpf_lsm_func_proto. This could be the first patch but don't feel strongly about it. > > Based on the discussion in [1], non-sleepable LSM programs should be > able to use bpf_spin_{lock, unlock}. > > Sleepable LSM programs can be preempted which means that allowng spin > locks will need more work (disabling preemption and the verifier > ensuring that no sleepable helpers are called when a spin lock is held). > > [1]: https://lore.kernel.org/bpf/20201103153132.2717326-1-kpsingh@chromium.org/T/#md601a053229287659071600d3483523f752cd2fb > > Signed-off-by: KP Singh <kpsingh@google.com> > --- > kernel/bpf/bpf_lsm.c | 4 ++++ > kernel/bpf/verifier.c | 17 +++++++++++++++++ > 2 files changed, 21 insertions(+) > > 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..7c6c246077cf 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; > + } It is good to have a more specific verifier log. However, these are duplicated checks (a few lines above in the same function). They should at least be removed. > + > + if (prog->aux->sleepable) { > + verbose(env, "sleepable progs cannot use bpf_spin_lock yet\n"); > + return -EINVAL; > + } > + } > + > if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) && > !bpf_offload_prog_map_match(prog, map)) { > verbose(env, "offload device mismatch between prog and map\n"); > -- > 2.29.1.341.ge80a0c044ae-goog >
On Wed, Nov 4, 2020 at 11:35 PM Martin KaFai Lau <kafai@fb.com> wrote: > > On Wed, Nov 04, 2020 at 05:44:49PM +0100, KP Singh wrote: > > From: KP Singh <kpsingh@google.com> > > > > Usage of spin locks was not allowed for tracing programs due to > > insufficient preemption checks. The verifier does not currently prevent > > LSM programs from using spin locks, but the helpers are not exposed > > via bpf_lsm_func_proto. > This could be the first patch but don't feel strongly about it. > > > > > Based on the discussion in [1], non-sleepable LSM programs should be > > able to use bpf_spin_{lock, unlock}. > > > > Sleepable LSM programs can be preempted which means that allowng spin > > locks will need more work (disabling preemption and the verifier > > ensuring that no sleepable helpers are called when a spin lock is held). > > > > [1]: https://lore.kernel.org/bpf/20201103153132.2717326-1-kpsingh@chromium.org/T/#md601a053229287659071600d3483523f752cd2fb > > > > Signed-off-by: KP Singh <kpsingh@google.com> > > --- > > kernel/bpf/bpf_lsm.c | 4 ++++ > > kernel/bpf/verifier.c | 17 +++++++++++++++++ > > 2 files changed, 21 insertions(+) > > > > 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..7c6c246077cf 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; > > + } > It is good to have a more specific verifier log. However, > these are duplicated checks (a few lines above in the same function). > They should at least be removed. > Thanks, I fixed this up and will move this as the first patch. > > + > > + if (prog->aux->sleepable) { > > + verbose(env, "sleepable progs cannot use bpf_spin_lock yet\n"); > > + return -EINVAL; > > + } > > + } > > + > > if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) && > > !bpf_offload_prog_map_match(prog, map)) { > > verbose(env, "offload device mismatch between prog and map\n"); > > -- > > 2.29.1.341.ge80a0c044ae-goog > >
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..7c6c246077cf 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 yet\n"); + return -EINVAL; + } + } + if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) && !bpf_offload_prog_map_match(prog, map)) { verbose(env, "offload device mismatch between prog and map\n");