bpf_get_[stack|stackid] on perf_events with precise_ip uses callchain attached to perf_sample_data. If this callchain is not presented, do not allow attaching BPF program that calls bpf_get_[stack|stackid] to this event.
In the error case, -EPROTO is returned so that libbpf can identify this error and print proper hint message. Signed-off-by: Song Liu <[email protected]> --- include/linux/filter.h | 3 ++- kernel/bpf/verifier.c | 3 +++ kernel/events/core.c | 18 ++++++++++++++++++ 3 files changed, 23 insertions(+), 1 deletion(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 1c6b6d982bf49..135692027dd8b 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -532,7 +532,8 @@ struct bpf_prog { is_func:1, /* program is a bpf function */ kprobe_override:1, /* Do we override a kprobe? */ has_callchain_buf:1, /* callchain buffer allocated? */ - enforce_expected_attach_type:1; /* Enforce expected_attach_type checking at attach time */ + enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */ + call_get_stack:1; /* Do we call bpf_get_stack() or bpf_get_stackid() */ enum bpf_prog_type type; /* Type of BPF program */ enum bpf_attach_type expected_attach_type; /* For some prog types */ u32 len; /* Number of filter blocks */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9a6703bc3f36f..41c9517a505ff 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4887,6 +4887,9 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn env->prog->has_callchain_buf = true; } + if (func_id == BPF_FUNC_get_stackid || func_id == BPF_FUNC_get_stack) + env->prog->call_get_stack = true; + if (changes_data) clear_all_pkt_pointers(env); return 0; diff --git a/kernel/events/core.c b/kernel/events/core.c index 856d98c36f562..ddcfd2fb5cc5a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9544,6 +9544,24 @@ static int perf_event_set_bpf_handler(struct perf_event *event, u32 prog_fd) if (IS_ERR(prog)) return PTR_ERR(prog); + if (event->attr.precise_ip && + prog->call_get_stack && + (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY) || + event->attr.exclude_callchain_kernel || + event->attr.exclude_callchain_user)) { + /* + * On perf_event with precise_ip, calling bpf_get_stack() + * may trigger unwinder warnings and occasional crashes. + * bpf_get_[stack|stackid] works around this issue by using + * callchain attached to perf_sample_data. If the + * perf_event does not full (kernel and user) callchain + * attached to perf_sample_data, do not allow attaching BPF + * program that calls bpf_get_[stack|stackid]. + */ + bpf_prog_put(prog); + return -EPROTO; + } + event->prog = prog; event->orig_overflow_handler = READ_ONCE(event->overflow_handler); WRITE_ONCE(event->overflow_handler, bpf_overflow_handler); -- 2.24.1
