[PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

Jiri Olsa
2022-09-27T20:33:12Z

Recent commit [1] changed branch stack data indication from
br_stack pointer to sample_flags in perf_sample_data struct.

We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
bit for valid branch stack data.

[1] a9a931e26668 ("perf: Use sample_flags for branch stack")

Cc: Kan Liang <kan.liang@linux.intel.com>
Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
NOTE sending on top of tip/master because [1] is not
merged in bpf-next/master yet

kernel/trace/bpf_trace.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 68e5cdd24cef..1fcd1234607e 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1507,6 +1507,9 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
if (unlikely(flags & ~BPF_F_GET_BRANCH_RECORDS_SIZE))
return -EINVAL;

+ if (unlikely(!(ctx->data->sample_flags & PERF_SAMPLE_BRANCH_STACK)))
+ return -ENOENT;
+
if (unlikely(!br_stack))
return -ENOENT;

--
2.37.3