[perf] vsyscall, possible circular locking dependency detected

From: Vince Weaver
Date: Wed Dec 13 2023 - 10:08:43 EST

Hello

I recently added vsyscall fuzzing support to the perf_fuzzer and it gave
me this dump when fuzzing on a haswell machine running current git
(6.7.0-rc5+)

[12559.226693] ======================================================
[12559.232906] WARNING: possible circular locking dependency detected
[12559.239116] 6.7.0-rc5+ #1 Tainted: G W
[12559.244286] ------------------------------------------------------
[12559.250493] perf_fuzzer/284551 is trying to acquire lock:
[12559.255923] ffff88800aff65d8 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x41/0x260
[12559.265034]
but task is already holding lock:
[12559.270891] ffff8880d08bd4d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0xb0
[12559.279463]
which lock already depends on the new lock.

[12559.287670]
the existing dependency chain (in reverse order) is:
[12559.295182]
-> #1 (&rq->__lock){-.-.}-{2:2}:
[12559.300966] _raw_spin_lock_nested+0x32/0x40
[12559.305789] raw_spin_rq_lock_nested+0x26/0xb0
[12559.310783] _raw_spin_rq_lock_irqsave+0x23/0x60
[12559.315959] sched_mm_cid_before_execve+0xcd/0x3d0
[12559.321306] exit_signals+0x1a3/0x450
[12559.325521] do_exit+0x24b/0x1100
[12559.329389] __x64_sys_exit+0x2c/0x30
[12559.333600] do_syscall_64+0x41/0x120
[12559.337814] entry_SYSCALL_64_after_hwframe+0x6e/0x76
[12559.343423]
-> #0 (&sighand->siglock){-.-.}-{2:2}:
[12559.349732] __lock_acquire+0x1d8d/0x31f0
[12559.354296] lock_acquire+0x16c/0x3e0
[12559.358506] _raw_spin_lock_irqsave+0x47/0x70
[12559.363416] force_sig_info_to_task+0x41/0x260
[12559.368418] force_sig_fault+0xaa/0xf0
[12559.372722] exc_page_fault+0x61/0xf0
[12559.376932] asm_exc_page_fault+0x22/0x30
[12559.381494] __get_user_handle_exception+0x0/0x20
[12559.386755] perf_callchain_user+0x2d3/0x390
[12559.391581] get_perf_callchain+0x21a/0x2d0
[12559.396312] perf_callchain+0xc3/0xe0
[12559.400526] perf_prepare_sample+0x4f1/0xc70
[12559.405346] perf_event_output_forward+0xbf/0x270
[12559.410599] __perf_event_overflow+0x1ad/0x3c0
[12559.415597] ___perf_sw_event+0x1f7/0x390
[12559.420154] __schedule+0x12d3/0x2560
[12559.424367] preempt_schedule_irq+0x47/0x90
[12559.429098] irqentry_exit+0x31/0x80
[12559.433223] asm_sysvec_apic_timer_interrupt+0x16/0x20
[12559.438912] seqcount_lockdep_reader_access.constprop.0+0x88/0x90
[12559.445562] ktime_get_real_ts64+0x28/0x120
[12559.450297] __x64_sys_gettimeofday+0x86/0x150
[12559.455292] emulate_vsyscall+0x258/0x590
[12559.459858] do_user_addr_fault+0x346/0x8c0
[12559.464588] exc_page_fault+0x61/0xf0
[12559.468798] asm_exc_page_fault+0x22/0x30
[12559.473360] _end+0x7a5da000/0x0
[12559.477135]
other info that might help us debug this:

[12559.485163] Possible unsafe locking scenario:

[12559.491115] CPU0 CPU1
[12559.495670] ---- ----
[12559.500228] lock(&rq->__lock);
[12559.503492] lock(&sighand->siglock);
[12559.509791] lock(&rq->__lock);
[12559.515569] lock(&sighand->siglock);
[12559.519352]
*** DEADLOCK ***

[12559.525303] 3 locks held by perf_fuzzer/284551:
[12559.529867] #0: ffff8880d08bd4d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0xb0
[12559.538873] #1: ffffffff831a3ec0 (rcu_read_lock){....}-{1:2}, at: ___perf_sw_event+0x10f/0x390
[12559.547618] #2: ffffffff831a3ec0 (rcu_read_lock){....}-{1:2}, at: perf_event_output_forward+0x8f/0x270
[12559.557058]
stack backtrace:
[12559.561439] CPU: 5 PID: 284551 Comm: perf_fuzzer Tainted: G W 6.7.0-rc5+ #1
[12559.569823] Hardware name: LENOVO 10AM000AUS/SHARKBAY, BIOS FBKT72AUS 01/26/2014
[12559.577248] Call Trace:
[12559.579720] <TASK>
[12559.581846] dump_stack_lvl+0x57/0x90
[12559.585539] check_noncircular+0x24f/0x290
[12559.589668] ? __pfx_check_noncircular+0x10/0x10
[12559.594327] ? lockdep_lock+0xb3/0x170
[12559.598106] ? __pfx_lockdep_lock+0x10/0x10
[12559.602323] ? add_chain_block+0x2dc/0x300
[12559.606456] __lock_acquire+0x1d8d/0x31f0
[12559.610508] ? __pfx___lock_acquire+0x10/0x10
[12559.614896] ? __pfx_mark_lock+0x10/0x10
[12559.618849] lock_acquire+0x16c/0x3e0
[12559.622548] ? force_sig_info_to_task+0x41/0x260
[12559.627197] ? __pfx_lock_acquire+0x10/0x10
[12559.631414] ? __pfx_mark_lock+0x10/0x10
[12559.635370] ? mark_lock+0x10b/0xd40
[12559.638981] ? mark_lock+0x10b/0xd40
[12559.642586] _raw_spin_lock_irqsave+0x47/0x70
[12559.646971] ? force_sig_info_to_task+0x41/0x260
[12559.651618] force_sig_info_to_task+0x41/0x260
[12559.656101] force_sig_fault+0xaa/0xf0
[12559.659882] ? __pfx_force_sig_fault+0x10/0x10
[12559.664360] ? kernelmode_fixup_or_oops+0x10a/0x150
[12559.669272] exc_page_fault+0x61/0xf0
[12559.672964] asm_exc_page_fault+0x22/0x30
[12559.677007] RIP: 0010:__get_user_handle_exception+0x0/0x20
[12559.682524] Code: 90 90 90 90 90 90 90 90 90 90 0f 1f 00 0f ae e8 48 8b 10 31 c0 0f 1f 00 c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 <0f> 1f 00 31 d2 48 c7 c0 f2 ff ff ff c3 cc cc cc cc cc cc cc cc cc
[12559.701336] RSP: 0000:ffffc90021bef5d0 EFLAGS: 00010006
[12559.706592] RAX: 0000000000000005 RBX: ffffc90021bef680 RCX: ffffffff8100a5a3
[12559.713764] RDX: 0000000000000011 RSI: ffffffff8100a55d RDI: ffff8880138d8090
[12559.720931] RBP: 0000000000000005 R08: 0000000000000000 R09: fffffbfff0799b5c
[12559.728098] R10: ffffffff83ccdae1 R11: 0000000000000000 R12: ffffc90021bef68c
[12559.735266] R13: ffffc90021bef688 R14: 0000000000000005 R15: ffff8880138d8000
[12559.742436] ? perf_callchain_user+0x353/0x390
[12559.746914] ? perf_callchain_user+0x30d/0x390
[12559.751391] perf_callchain_user+0x2d3/0x390
[12559.755699] get_perf_callchain+0x21a/0x2d0
[12559.759917] ? __pfx_get_perf_callchain+0x10/0x10
[12559.764662] ? lock_is_held_type+0xe3/0x140
[12559.768882] ? preempt_schedule_irq+0x47/0x90
[12559.773269] perf_callchain+0xc3/0xe0
[12559.776961] perf_prepare_sample+0x4f1/0xc70
[12559.781263] ? __pfx_perf_prepare_sample+0x10/0x10
[12559.786084] ? __pfx___lock_acquire+0x10/0x10
[12559.790478] perf_event_output_forward+0xbf/0x270
[12559.795214] ? __pfx_perf_event_output_forward+0x10/0x10
[12559.800554] ? lock_acquire+0x16c/0x3e0
[12559.804420] ? lock_acquire+0x17c/0x3e0
[12559.808295] ? __pfx_lock_acquire+0x10/0x10
[12559.812511] ? ___perf_sw_event+0x22f/0x390
[12559.816727] ? __pfx_lock_release+0x10/0x10
[12559.820951] __perf_event_overflow+0x1ad/0x3c0
[12559.825428] ___perf_sw_event+0x1f7/0x390
[12559.829467] ? __pfx____perf_sw_event+0x10/0x10
[12559.834037] ? preempt_schedule_irq+0x47/0x90
[12559.838426] ? __update_load_avg_se+0x86/0x5c0
[12559.842900] ? __update_load_avg_cfs_rq+0x70/0x570
[12559.847726] ? lock_acquire+0x16c/0x3e0
[12559.851590] ? __update_load_avg_se+0x15f/0x5c0
[12559.856154] ? lock_is_held_type+0xe3/0x140
[12559.860372] ? update_load_avg+0x154/0xdc0
[12559.864499] ? lock_is_held_type+0xe3/0x140
[12559.868721] ? set_next_entity+0xec/0x1e0
[12559.872764] ? preempt_schedule_irq+0x47/0x90
[12559.877149] ? __schedule+0x12d3/0x2560
[12559.881012] __schedule+0x12d3/0x2560
[12559.884717] ? __pfx___schedule+0x10/0x10
[12559.888754] ? __pfx___lock_acquire+0x10/0x10
[12559.893139] ? lock_is_held_type+0xe3/0x140
[12559.897353] ? mark_held_locks+0x24/0x90
[12559.901316] preempt_schedule_irq+0x47/0x90
[12559.905531] irqentry_exit+0x31/0x80
[12559.909136] asm_sysvec_apic_timer_interrupt+0x16/0x20
[12559.914305] RIP: 0010:seqcount_lockdep_reader_access.constprop.0+0x88/0x90
[12559.921217] Code: 31 f6 48 c7 c7 48 7c 1c 83 e8 84 25 f8 ff 48 8b 74 24 08 48 c7 c7 48 7c 1c 83 e8 93 1c f8 ff e8 6e d2 0c 00 fb 0f 1f 44 00 00 <5a> c3 cc cc cc cc 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
[12559.940025] RSP: 0000:ffffc90021befdb8 EFLAGS: 00000202
[12559.945281] RAX: 000000000182a8d9 RBX: ffffc90021befe18 RCX: dffffc0000000000
[12559.952453] RDX: 0000000000000000 RSI: ffffffff826804e0 RDI: ffffffff828c8620
[12559.959619] RBP: 00007ffcf0f36fd0 R08: 0000000000000001 R09: 0000000000000001
[12559.966786] R10: ffffffff8371fd27 R11: 0000000000000000 R12: 0000000000000000
[12559.973953] R13: 0000000000000000 R14: ffff88800aa55340 R15: ffffc90021befff0
[12559.981129] ? seqcount_lockdep_reader_access.constprop.0+0x82/0x90
[12559.987426] ? ktime_get_real_ts64+0x28/0x120
[12559.991820] ktime_get_real_ts64+0x28/0x120
[12559.996032] __x64_sys_gettimeofday+0x86/0x150
[12560.000512] ? __pfx___x64_sys_gettimeofday+0x10/0x10
[12560.005602] ? do_user_addr_fault+0x3c5/0x8c0
[12560.009994] emulate_vsyscall+0x258/0x590
[12560.014034] ? 0xffffffffff600000
[12560.017376] do_user_addr_fault+0x346/0x8c0
[12560.021587] ? rcu_is_watching+0x34/0x60
[12560.025541] ? 0xffffffffff600000
[12560.028882] exc_page_fault+0x61/0xf0
[12560.032578] asm_exc_page_fault+0x22/0x30
[12560.036616] RIP: 0033:_end+0x7a5da000/0x0
[12560.040653] Code: Unable to access opcode bytes at 0xffffffffff5fffd6.
[12560.047210] RSP: 002b:00007ffcf0f36fb8 EFLAGS: 00010246
[12560.052470] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 000000000000000a
[12560.059632] RDX: 0000000000000010 RSI: 0000000000000000 RDI: 00007ffcf0f36fd0
[12560.066799] RBP: 00007ffcf0f36fc0 R08: 00007f482684b274 R09: 00007f482684b280
[12560.073966] R10: 00007f4826675a10 R11: 0000000000000246 R12: 0000000000000000
[12560.081132] R13: 00007ffcf0f39448 R14: 000055f2641d2dd8 R15: 00007f48268a3000
[12560.088304] </TASK>