6.8-stable review patch. If anyone has any objections, please let me know.
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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 95cd8414f6ef8..e5d78565f479f 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -289,6 +289,7 @@ 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 */ @@ -310,7 +311,9 @@ 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: