[PATCH 6.6 063/158] perf lock contention: Add a missing NULL check

Greg Kroah-Hartman
2024-04-23T21:43:19Z

From: Namhyung Kim <namhyung@kernel.org>

[ Upstream commit f3408580bac8ce5cd76e7391e529c0a22e7c7eb2 ]

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

Fixes: 1811e82767dcc ("perf lock contention: Track and show siglock with address")
Reviewed-by: Ian Rogers <irogers@google.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240409225542.1870999-1-namhyung@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/bpf_skel/lock_contention.bpf.c | 5 ++++-
1 file changed, 4 insertions(+), 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 8d3cfbb3cc65b..473106c72c695 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -238,6 +238,7 @@ static inline __u32 check_lock_type(__u64 lock, __u32 flags)
struct task_struct *curr;
struct mm_struct___old *mm_old;
struct mm_struct___new *mm_new;
+ struct sighand_struct *sighand;

switch (flags) {
case LCB_F_READ: /* rwsem */
@@ -259,7 +260,9 @@ 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)
+ sighand = curr->sighand;
+
+ if (sighand && &sighand->siglock == (void *)lock)
return LCD_F_SIGHAND_LOCK;
break;
default:
--
2.43.0