bpf: set maximum number of attached progs to 64 for a single perf tp

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

Fixes: e87c6bc3852b ("bpf: permit multiple bpf attachments for a single perf event")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

2 files changed, 10 insertions, 1 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index b9f8686a84cf..86b50aa26ee8 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 27d1f4ffa3de..0ce99c379c30 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;