[PATCH net 1/2] bpf: set maximum number of attached progs to 64 for a single perf tp

[Yonghong Song]

cgropu+bpf prog array has a maximum number of 64 programs.
Let us apply the same limit here.

Signed-off-by: Yonghong Song <y...@fb.com>
---
 kernel/bpf/core.c        | 3 ++-
 kernel/trace/bpf_trace.c | 8 ++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index b9f8686..86b50aa 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1447,7 +1447,8 @@ int bpf_prog_array_length(struct bpf_prog_array __rcu 
*progs)
        rcu_read_lock();
        prog = rcu_dereference(progs)->progs;
        for (; *prog; prog++)
-               cnt++;
+               if (*prog != &dummy_bpf_prog.prog)
+                       cnt++;
        rcu_read_unlock();
        return cnt;
 }
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 27d1f4f..0ce99c3 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -759,6 +759,8 @@ const struct bpf_prog_ops perf_event_prog_ops = {
 
 static DEFINE_MUTEX(bpf_event_mutex);
 
+#define BPF_TRACE_MAX_PROGS 64
+
 int perf_event_attach_bpf_prog(struct perf_event *event,
                               struct bpf_prog *prog)
 {
@@ -772,6 +774,12 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
                goto unlock;
 
        old_array = event->tp_event->prog_array;
+       if (old_array &&
+           bpf_prog_array_length(old_array) >= BPF_TRACE_MAX_PROGS) {
+               ret = -E2BIG;
+               goto unlock;
+       }
+
        ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
        if (ret < 0)
                goto unlock;
-- 
2.9.5