syzbot

INFO: task syz.1.999:9797 blocked in I/O wait for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.999       state:D stack:25808 pid:9797  tgid:9795  ppid:5609   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7326
 io_schedule+0x8a/0xf0 kernel/sched/core.c:8154
 folio_wait_bit_common+0x414/0xa70 mm/filemap.c:1323
 folio_lock include/linux/pagemap.h:1157 [inline]
 migrate_folio_unmap mm/migrate.c:1250 [inline]
 migrate_pages_batch+0x7a1/0x45c0 mm/migrate.c:1907
 migrate_pages_sync+0x4db/0x880 mm/migrate.c:2051
 migrate_pages+0x1a83/0x2850 mm/migrate.c:2133
 compact_zone+0x243c/0x4420 mm/compaction.c:2668
 compact_node+0x17f/0x2c0 mm/compaction.c:2937
 compact_nodes mm/compaction.c:2959 [inline]
 sysctl_compaction_handler mm/compaction.c:3010 [inline]
 sysctl_compaction_handler+0x141/0x210 mm/compaction.c:2997
 proc_sys_call_handler+0x47f/0x5a0 fs/proc/proc_sysctl.c:600
 iter_file_splice_write+0x830/0x10b0 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x192/0x690 fs/splice.c:1159
 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x174/0x240 fs/splice.c:1228
 do_sendfile+0xadc/0xe20 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1426 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x154/0x220 fs/read_write.c:1418
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc83ab9de59
RSP: 002b:00007fc83b987028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fc83ae25fa0 RCX: 00007fc83ab9de59
RDX: 00002000000000c0 RSI: 0000000000000006 RDI: 0000000000000008
RBP: 00007fc83ac33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000000a R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc83ae26038 R14: 00007fc83ae25fa0 R15: 00007fff655f52e8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
 #0: ffffffff8ebe6100 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8ebe6100 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8ebe6100 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
4 locks held by dhcpcd/5273:
2 locks held by getty/5367:
 #0: ffff8880343460a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
1 lock held by udevd/5938:
 #0: ffff888028609350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0x41a/0xe40 block/bdev.c:948
1 lock held by syz.1.999/9797:
 #0: ffff888055df2450 (sb_writers#3){.+.+}-{0:0}, at: splice_direct_to_actor+0x345/0xa30 fs/splice.c:1103
1 lock held by syz.0.2090/13396:
3 locks held by syz.2.2092/13407:
4 locks held by syz.2.2094/13414:
 #0: ffff888034bbc0a0 (&tty->ldisc_sem){++++}-{0:0}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:289 [inline]
 #0: ffff888034bbc0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:335 [inline]
 #0: ffff888034bbc0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:366 [inline]
 #0: ffff888034bbc0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_release+0x154/0x2f0 drivers/tty/tty_ldisc.c:780
 #1: ffff888034bbf0a0 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: __tty_ldisc_lock_nested drivers/tty/tty_ldisc.c:295 [inline]
 #1: ffff888034bbf0a0 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:337 [inline]
 #1: ffff888034bbf0a0 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:366 [inline]
 #1: ffff888034bbf0a0 (&tty->ldisc_sem/1){+.+.}-{0:0}, at: tty_ldisc_release+0x182/0x2f0 drivers/tty/tty_ldisc.c:780
 #2: ffffffff90a9b480 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff90a9b480 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_dev_lock+0x146/0x360 net/core/dev.c:2163
 #3: ffffffff8ebf1ba8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x27f/0x3c0 kernel/rcu/tree_exp.h:311

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:122
 nmi_trigger_cpumask_backtrace+0x21c/0x2a0 lib/nmi_backtrace.c:65
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xcb1/0x1030 kernel/hung_task.c:561
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 5273 Comm: dhcpcd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
RIP: 0010:__sanitizer_cov_trace_pc+0x3f/0x70 kernel/kcov.c:217
Code: 59 12 a9 00 01 ff 00 74 1b f6 c4 01 74 07 a9 00 00 ff 00 74 05 c3 cc cc cc cc 8b 82 24 17 00 00 85 c0 74 f1 8b 82 f8 16 00 00 <83> f8 02 75 e6 48 8b 8a 00 17 00 00 8b 92 fc 16 00 00 48 8b 01 48
RSP: 0018:ffffc90002effee8 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff8880286d0000 RCX: ffffffff81add243
RDX: ffff8880286d0000 RSI: ffffffff81add25c RDI: ffff8880286d0000
RBP: ffff8880286d1a40 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880286d0000
R13: 0000000000000000 R14: 0000000000000000 R15: 000000000000010f
FS:  00007f504a2dc780(0000) GS:ffff888123eec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000b40030 CR3: 00000000348b3000 CR4: 00000000003526f0
DR0: 000004000002002c DR1: fffeffffff7fff02 DR2: 0000000080000002
DR3: 0000000000000003 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 test_ti_thread_flag include/linux/thread_info.h:133 [inline]
 fpregs_assert_state_consistent+0x6c/0x150 arch/x86/kernel/fpu/core.c:912
 arch_exit_to_user_mode_prepare arch/x86/include/asm/entry-common.h:63 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:210 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x183/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f504a366407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffe7986c5f0 EFLAGS: 00000202 ORIG_RAX: 000000000000010f
RAX: 0000000000000001 RBX: 00007f504a2dc780 RCX: 00007f504a366407
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 00005600f103a4a0
RBP: 00007ffe7986c930 R08: 0000000000000008 R09: 0000000000000000
R10: 00007ffe7986c930 R11: 0000000000000202 R12: 00005600ceac65e0
R13: 00005600f1034d40 R14: 0000000000000000 R15: 00007ffe7986c6e0
 </TASK>