On Sat, 23 Nov 2024 21:27:44 +0100 Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Sat, Nov 23, 2024 at 03:39:45AM +0000, Ruan Bonan wrote: > > > </TASK> > > FAULT_INJECTION: forcing a failure. > > name fail_usercopy, interval 1, probability 0, space 0, times 0 > > ====================================================== > > WARNING: possible circular locking dependency detected > > 6.12.0-rc7-00144-g66418447d27b #8 Not tainted > > ------------------------------------------------------ > > syz-executor144/330 is trying to acquire lock: > > ffffffffbcd2da38 ((console_sem).lock){....}-{2:2}, at: down_trylock+0x20/0xa0 kernel/locking/semaphore.c:139 > > > > but task is already holding lock: > > ffff888065cbd718 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:598 [inline] > > ffff888065cbd718 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock kernel/sched/sched.h:1506 [inline] > > ffff888065cbd718 (&rq->__lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1805 [inline] > > ffff888065cbd718 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0x140/0x1e70 kernel/sched/core.c:6592 > > > > which lock already depends on the new lock. > > > > _printk+0x7a/0xa0 kernel/printk/printk.c:2432 > > fail_dump lib/fault-inject.c:46 [inline] > > should_fail_ex+0x3be/0x570 lib/fault-inject.c:154 > > strncpy_from_user+0x36/0x230 lib/strncpy_from_user.c:118 > > strncpy_from_user_nofault+0x71/0x140 mm/maccess.c:186 > > bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:215 [inline] > > ____bpf_probe_read_user_str kernel/trace/bpf_trace.c:224 [inline] > > bpf_probe_read_user_str+0x2a/0x70 kernel/trace/bpf_trace.c:221 > > bpf_prog_bc7c5c6b9645592f+0x3e/0x40 > > bpf_dispatcher_nop_func include/linux/bpf.h:1265 [inline] > > __bpf_prog_run include/linux/filter.h:701 [inline] > > bpf_prog_run include/linux/filter.h:708 [inline] > > __bpf_trace_run kernel/trace/bpf_trace.c:2316 [inline] > > bpf_trace_run4+0x30b/0x4d0 kernel/trace/bpf_trace.c:2359 > > __bpf_trace_sched_switch+0x1c6/0x2c0 include/trace/events/sched.h:222 > > trace_sched_switch+0x12a/0x190 include/trace/events/sched.h:222 > > -EWONTFIX. Don't do stupid. Ack. BPF should not be causing deadlocks by doing code called from tracepoints. Tracepoints have a special context similar to NMIs. If you add a hook into an NMI handler that causes a deadlock, it's a bug in the hook, not the NMI code. If you add code that causes a deadlock when attaching to a tracepoint, it's a bug in the hook, not the tracepoint. -- Steve