On Tue, Apr 2, 2024 at 11:45 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > I got a report for a failure in BPF verifier on a recent kernel with > perf lock contention command. It checks task->sighand->siglock without > checking if sighand is NULL or not. Let's add one. > > ; if (&curr->sighand->siglock == (void *)lock) > 265: (79) r1 = *(u64 *)(r0 +2624) ; frame1: R0_w=trusted_ptr_task_struct(off=0,imm=0) R1_w=rcu_ptr_or_null_sighand_struct(off=0,imm=0) > 266: (b7) r2 = 0 ; frame1: R2_w=0 > 267: (0f) r1 += r2 > R1 pointer arithmetic on rcu_ptr_or_null_ prohibited, null-check it first > processed 164 insns (limit 1000000) max_states_per_insn 1 total_states 15 peak_states 15 mark_read 5 > -- END PROG LOAD LOG -- > libbpf: prog 'contention_end': failed to load: -13 > libbpf: failed to load object 'lock_contention_bpf' > libbpf: failed to load BPF skeleton 'lock_contention_bpf': -13 > Failed to load lock-contention BPF skeleton > lock contention BPF setup failed > lock contention did not detect any lock contention > > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx> Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx> Thanks, Ian > --- > tools/perf/util/bpf_skel/lock_contention.bpf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c > index fb54bd38e7d0..4e5914d7eeaa 100644 > --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c > +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c > @@ -305,7 +305,7 @@ static inline __u32 check_lock_type(__u64 lock, __u32 flags) > break; > case LCB_F_SPIN: /* spinlock */ > curr = bpf_get_current_task_btf(); > - if (&curr->sighand->siglock == (void *)lock) > + if (curr->sighand && &curr->sighand->siglock == (void *)lock) > return LCD_F_SIGHAND_LOCK; > break; > default: > -- > 2.44.0.478.gd926399ef9-goog >
