[syzbot] [trace?] [bpf?] possible deadlock in __mod_timer (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a940d9a43e62 Merge tag 'soc-arm-6.12' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12d1c69f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=44d46e514184cd24
dashboard link: https://syzkaller.appspot.com/bug?extid=83a876aef81c9a485ae8
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11597677980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13cd7500580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-a940d9a4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e9929bfe422c/vmlinux-a940d9a4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a6c74ee261ed/bzImage-a940d9a4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+83a876...@syzkaller.appspotmail.com

FAULT_INJECTION: forcing a failure.
name fail_usercopy, interval 1, probability 0, space 0, times 1
======================================================
WARNING: possible circular locking dependency detected
6.11.0-syzkaller-03917-ga940d9a43e62 #0 Not tainted
------------------------------------------------------
syz-executor291/5332 is trying to acquire lock:
ffffffff8dda88d8 ((console_sem).lock){-...}-{2:2}, at: down_trylock+0x12/0x70 kernel/locking/semaphore.c:139

but task is already holding lock:
ffff88806a92a858 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x6c1/0xdc0 kernel/time/timer.c:1164

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&base->lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
lock_timer_base+0x5d/0x220 kernel/time/timer.c:1051
__mod_timer+0x426/0xdc0 kernel/time/timer.c:1132
add_timer_global+0x8a/0xc0 kernel/time/timer.c:1330
__queue_delayed_work+0x1ba/0x2e0 kernel/workqueue.c:2525
queue_delayed_work_on+0x12a/0x150 kernel/workqueue.c:2554
psi_task_change+0x1b4/0x2e0 kernel/sched/psi.c:913
psi_enqueue kernel/sched/stats.h:143 [inline]
enqueue_task+0x1a5/0x350 kernel/sched/core.c:1975
activate_task kernel/sched/core.c:2009 [inline]
wake_up_new_task+0x5ba/0xd30 kernel/sched/core.c:4689
kernel_clone+0x236/0x960 kernel/fork.c:2812
user_mode_thread+0xb4/0xf0 kernel/fork.c:2859
rest_init+0x23/0x2b0 init/main.c:712
start_kernel+0x3e4/0x4d0 init/main.c:1105
x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:507
x86_64_start_kernel+0xb2/0xc0 arch/x86/kernel/head64.c:488
common_startup_64+0x13e/0x148

-> #2 (&rq->__lock){-.-.}-{2:2}:
_raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378
raw_spin_rq_lock_nested+0x29/0x130 kernel/sched/core.c:560
raw_spin_rq_lock kernel/sched/sched.h:1415 [inline]
rq_lock kernel/sched/sched.h:1714 [inline]
task_fork_fair+0x73/0x250 kernel/sched/fair.c:12710
sched_cgroup_fork+0x3cf/0x510 kernel/sched/core.c:4633
copy_process+0x439b/0x8dd0 kernel/fork.c:2483
kernel_clone+0xfd/0x960 kernel/fork.c:2781
user_mode_thread+0xb4/0xf0 kernel/fork.c:2859
rest_init+0x23/0x2b0 init/main.c:712
start_kernel+0x3e4/0x4d0 init/main.c:1105
x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:507
x86_64_start_kernel+0xb2/0xc0 arch/x86/kernel/head64.c:488
common_startup_64+0x13e/0x148

-> #1 (&p->pi_lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]
try_to_wake_up+0x9a/0x13e0 kernel/sched/core.c:4051
up+0x79/0xb0 kernel/locking/semaphore.c:191
__up_console_sem+0x85/0xe0 kernel/printk/printk.c:343
__console_unlock kernel/printk/printk.c:2844 [inline]
__console_flush_and_unlock kernel/printk/printk.c:3241 [inline]
console_unlock+0x1dc/0x210 kernel/printk/printk.c:3279
vga_remove_vgacon drivers/pci/vgaarb.c:186 [inline]
vga_remove_vgacon+0x90/0xd0 drivers/pci/vgaarb.c:167
__aperture_remove_legacy_vga_devices drivers/video/aperture.c:331 [inline]
aperture_remove_conflicting_pci_devices+0x16a/0x1e0 drivers/video/aperture.c:369
virtio_gpu_pci_quirk drivers/gpu/drm/virtio/virtgpu_drv.c:61 [inline]
virtio_gpu_probe+0x408/0x4e0 drivers/gpu/drm/virtio/virtgpu_drv.c:92
virtio_dev_probe+0x586/0x8a0 drivers/virtio/virtio.c:341
call_driver_probe drivers/base/dd.c:578 [inline]
really_probe+0x23e/0xa90 drivers/base/dd.c:657
__driver_probe_device+0x1de/0x440 drivers/base/dd.c:799
driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:829
__driver_attach+0x283/0x580 drivers/base/dd.c:1215
bus_for_each_dev+0x13c/0x1d0 drivers/base/bus.c:368
bus_add_driver+0x2e9/0x690 drivers/base/bus.c:673
driver_register+0x15c/0x4b0 drivers/base/driver.c:246
do_one_initcall+0x128/0x700 init/main.c:1269
do_initcall_level init/main.c:1331 [inline]
do_initcalls init/main.c:1347 [inline]
do_basic_setup init/main.c:1366 [inline]
kernel_init_freeable+0x69d/0xca0 init/main.c:1580
kernel_init+0x1c/0x2b0 init/main.c:1469
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 ((console_sem).lock){-...}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3158 [inline]
check_prevs_add kernel/locking/lockdep.c:3277 [inline]
validate_chain kernel/locking/lockdep.c:3901 [inline]
__lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5199
lock_acquire kernel/locking/lockdep.c:5822 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5787
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
down_trylock+0x12/0x70 kernel/locking/semaphore.c:139
__down_trylock_console_sem+0x40/0x140 kernel/printk/printk.c:326
console_trylock kernel/printk/printk.c:2827 [inline]
console_trylock_spinning kernel/printk/printk.c:1990 [inline]
vprintk_emit+0x3ec/0x6f0 kernel/printk/printk.c:2406
vprintk+0x7f/0xa0 kernel/printk/printk_safe.c:68
_printk+0xc8/0x100 kernel/printk/printk.c:2432
fail_dump lib/fault-inject.c:45 [inline]
should_fail_ex+0x46c/0x5b0 lib/fault-inject.c:153
strncpy_from_user+0x38/0x320 lib/strncpy_from_user.c:118
strncpy_from_user_nofault+0x7f/0x180 mm/maccess.c:186
bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:216 [inline]
____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:311 [inline]
bpf_probe_read_compat_str+0xf1/0x170 kernel/trace/bpf_trace.c:307
bpf_prog_d0e9ac47b081aec3+0x48/0x4a
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_timer_start+0xc7/0x100 include/trace/events/timer.h:52
trace_timer_start include/trace/events/timer.h:52 [inline]
enqueue_timer+0x2b4/0x550 kernel/time/timer.c:663
internal_add_timer kernel/time/timer.c:688 [inline]
__mod_timer+0x8d7/0xdc0 kernel/time/timer.c:1183
add_timer_global+0x8a/0xc0 kernel/time/timer.c:1330
__queue_delayed_work+0x1ba/0x2e0 kernel/workqueue.c:2525
queue_delayed_work_on+0x12a/0x150 kernel/workqueue.c:2554
queue_delayed_work include/linux/workqueue.h:636 [inline]
fbcon_add_cursor_work drivers/video/fbdev/core/fbcon.c:392 [inline]
fbcon_cursor+0x4a0/0x520 drivers/video/fbdev/core/fbcon.c:1316
hide_cursor+0x84/0x220 drivers/tty/vt/vt.c:846
do_con_write+0x21e6/0x7bb0 drivers/tty/vt/vt.c:3068
con_write+0x23/0xb0 drivers/tty/vt/vt.c:3434
process_output_block drivers/tty/n_tty.c:574 [inline]
n_tty_write+0x419/0x1140 drivers/tty/n_tty.c:2389
iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
file_tty_write.constprop.0+0x506/0x9a0 drivers/tty/tty_io.c:1096
new_sync_write fs/read_write.c:590 [inline]
vfs_write+0x6b5/0x1140 fs/read_write.c:683
ksys_write+0x12f/0x260 fs/read_write.c:736
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
(console_sem).lock --> &rq->__lock --> &base->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&base->lock);
lock(&rq->__lock);
lock(&base->lock);
lock((console_sem).lock);

*** DEADLOCK ***

7 locks held by syz-executor291/5332:
#0: ffff8880353610a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffff888035361130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:954 [inline]
#1: ffff888035361130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: iterate_tty_write drivers/tty/tty_io.c:973 [inline]
#1: ffff888035361130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x281/0x9a0 drivers/tty/tty_io.c:1096
#2: ffff8880353612e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1bd/0x1140 drivers/tty/n_tty.c:2372
#3: ffffc9000324e380 (&ldata->output_lock){+.+.}-{3:3}, at: process_output_block drivers/tty/n_tty.c:529 [inline]
#3: ffffc9000324e380 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0x533/0x1140 drivers/tty/n_tty.c:2389
#4: ffffffff8dda8460 (console_lock){+.+.}-{0:0}, at: do_con_write+0x154/0x7bb0 drivers/tty/vt/vt.c:3056
#5: ffff88806a92a858 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x6c1/0xdc0 kernel/time/timer.c:1164
#6: ffffffff8ddbaea0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
#6: ffffffff8ddbaea0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#6: ffffffff8ddbaea0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2405 [inline]
#6: ffffffff8ddbaea0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2447

stack backtrace:
CPU: 3 UID: 0 PID: 5332 Comm: syz-executor291 Not tainted 6.11.0-syzkaller-03917-ga940d9a43e62 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2203
check_prev_add kernel/locking/lockdep.c:3158 [inline]
check_prevs_add kernel/locking/lockdep.c:3277 [inline]
validate_chain kernel/locking/lockdep.c:3901 [inline]
__lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5199
lock_acquire kernel/locking/lockdep.c:5822 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5787
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
down_trylock+0x12/0x70 kernel/locking/semaphore.c:139
__down_trylock_console_sem+0x40/0x140 kernel/printk/printk.c:326
console_trylock kernel/printk/printk.c:2827 [inline]
console_trylock_spinning kernel/printk/printk.c:1990 [inline]
vprintk_emit+0x3ec/0x6f0 kernel/printk/printk.c:2406
vprintk+0x7f/0xa0 kernel/printk/printk_safe.c:68
_printk+0xc8/0x100 kernel/printk/printk.c:2432
fail_dump lib/fault-inject.c:45 [inline]
should_fail_ex+0x46c/0x5b0 lib/fault-inject.c:153
strncpy_from_user+0x38/0x320 lib/strncpy_from_user.c:118
strncpy_from_user_nofault+0x7f/0x180 mm/maccess.c:186
bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:216 [inline]
____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:311 [inline]
bpf_probe_read_compat_str+0xf1/0x170 kernel/trace/bpf_trace.c:307
bpf_prog_d0e9ac47b081aec3+0x48/0x4a
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_timer_start+0xc7/0x100 include/trace/events/timer.h:52
trace_timer_start include/trace/events/timer.h:52 [inline]
enqueue_timer+0x2b4/0x550 kernel/time/timer.c:663
internal_add_timer kernel/time/timer.c:688 [inline]
__mod_timer+0x8d7/0xdc0 kernel/time/timer.c:1183
add_timer_global+0x8a/0xc0 kernel/time/timer.c:1330
__queue_delayed_work+0x1ba/0x2e0 kernel/workqueue.c:2525
queue_delayed_work_on+0x12a/0x150 kernel/workqueue.c:2554
queue_delayed_work include/linux/workqueue.h:636 [inline]
fbcon_add_cursor_work drivers/video/fbdev/core/fbcon.c:392 [inline]
fbcon_cursor+0x4a0/0x520 drivers/video/fbdev/core/fbcon.c:1316
hide_cursor+0x84/0x220 drivers/tty/vt/vt.c:846
do_con_write+0x21e6/0x7bb0 drivers/tty/vt/vt.c:3068
con_write+0x23/0xb0 drivers/tty/vt/vt.c:3434
process_output_block drivers/tty/n_tty.c:574 [inline]
n_tty_write+0x419/0x1140 drivers/tty/n_tty.c:2389
iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
file_tty_write.constprop.0+0x506/0x9a0 drivers/tty/tty_io.c:1096
new_sync_write fs/read_write.c:590 [inline]
vfs_write+0x6b5/0x1140 fs/read_write.c:683
ksys_write+0x12f/0x260 fs/read_write.c:736
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f36b5809869
Code: 48 83 c4 28 c3 e8 17 1a 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeb8b42888 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffeb8b42890 RCX: 00007f36b5809869
RDX: 0000000000001006 RSI: 0000000020001040 RDI: 0000000000000006
RBP: 0000000000000001 R08: 00007ffeb8b42627 R09: 00007f36b5870033
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffeb8b42a68 R14: 0000000000000001 R15: 0000000000000001
</TASK>
CPU: 3 UID: 0 PID: 5332 Comm: syz-executor291 Not tainted 6.11.0-syzkaller-03917-ga940d9a43e62 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
fail_dump lib/fault-inject.c:52 [inline]
should_fail_ex+0x497/0x5b0 lib/fault-inject.c:153
strncpy_from_user+0x38/0x320 lib/strncpy_from_user.c:118
strncpy_from_user_nofault+0x7f/0x180 mm/maccess.c:186
bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:216 [inline]
____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:311 [inline]
bpf_probe_read_compat_str+0xf1/0x170 kernel/trace/bpf_trace.c:307
bpf_prog_d0e9ac47b081aec3+0x48/0x4a
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2406 [inline]
bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2447
__bpf_trace_timer_start+0xc7/0x100 include/trace/events/timer.h:52
trace_timer_start include/trace/events/timer.h:52 [inline]
enqueue_timer+0x2b4/0x550 kernel/time/timer.c:663
internal_add_timer kernel/time/timer.c:688 [inline]
__mod_timer+0x8d7/0xdc0 kernel/time/timer.c:1183
add_timer_global+0x8a/0xc0 kernel/time/timer.c:1330
__queue_delayed_work+0x1ba/0x2e0 kernel/workqueue.c:2525
queue_delayed_work_on+0x12a/0x150 kernel/workqueue.c:2554
queue_delayed_work include/linux/workqueue.h:636 [inline]
fbcon_add_cursor_work drivers/video/fbdev/core/fbcon.c:392 [inline]
fbcon_cursor+0x4a0/0x520 drivers/video/fbdev/core/fbcon.c:1316
hide_cursor+0x84/0x220 drivers/tty/vt/vt.c:846
do_con_write+0x21e6/0x7bb0 drivers/tty/vt/vt.c:3068
con_write+0x23/0xb0 drivers/tty/vt/vt.c:3434
process_output_block drivers/tty/n_tty.c:574 [inline]
n_tty_write+0x419/0x1140 drivers/tty/n_tty.c:2389
iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
file_tty_write.constprop.0+0x506/0x9a0 drivers/tty/tty_io.c:1096
new_sync_write fs/read_write.c:590 [inline]
vfs_write+0x6b5/0x1140 fs/read_write.c:683
ksys_write+0x12f/0x260 fs/read_write.c:736
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f36b5809869
Code: 48 83 c4 28 c3 e8 17 1a 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeb8b42888 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffeb8b42890 RCX: 00007f36b5809869
RDX: 0000000000001006 RSI: 0000000020001040 RDI: 0000000000000006
RBP: 0000000000000001 R08: 00007ffeb8b42627 R09: 00007f36b5870033
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffeb8b42a68 R14: 0000000000000001 R15: 0000000000000001
</TASK>


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[Steven Rostedt]

I'm assuming that lockdep splats like this will no longer be an issue come 6.12?

-- Steve

[Petr Mladek]

I am afraid that it still would happen in 6.12. :-(

The legacy loop (console_trylock()/unlock()) will still be called
there when there is a boot or a legacy console registered.

I actually guess that all console will be legacy in 6.12 because
the conversion of the uart 8250 console driver still need some love,
see the last version at
https://lore.kernel.org/r/20240913140538.22...@linutronix.de

The only exception will be CONFIG_RT mode which would offload even
the legacy loop to a dedicated kthread.

Best Regards,
Petr