Kernel bug: INFO: task hung in exit_mmap (2)
Subsystem: mm
Status: open

Crash report:
INFO: task syz-executor253:8529 blocked for more than 143 seconds.
      Not tainted 6.15.0-rc2-syzkaller-00258-g750d0ac001e8 #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor253 state:D stack:24424 pid:8529  tgid:8527  ppid:5850   task_flags:0x40054c flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x1b88/0x5240 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0x163/0x360 kernel/sched/core.c:6860
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6917
 rwsem_down_write_slowpath+0xedd/0x1420 kernel/locking/rwsem.c:1176
 __down_write_common kernel/locking/rwsem.c:1304 [inline]
 __down_write kernel/locking/rwsem.c:1313 [inline]
 down_write+0x1da/0x220 kernel/locking/rwsem.c:1578
 mmap_write_lock include/linux/mmap_lock.h:128 [inline]
 exit_mmap+0x305/0xde0 mm/mmap.c:1292
 __mmput+0x115/0x420 kernel/fork.c:1379
 exit_mm+0x221/0x310 kernel/exit.c:589
 do_exit+0x994/0x27f0 kernel/exit.c:940
 do_group_exit+0x207/0x2c0 kernel/exit.c:1102
 get_signal+0x1696/0x1730 kernel/signal.c:3034
 arch_do_signal_or_restart+0x98/0x810 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xce/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x210 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0e7faaa6e9
RSP: 002b:00007f0e7fa42218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f0e7fb34338 RCX: 00007f0e7faaa6e9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f0e7fb34338
RBP: 00007f0e7fb34330 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0e7fb01074
R13: 0000200000000040 R14: 00002000000002c0 R15: 00002000000002c8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8ed3df20 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8ed3df20 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8ed3df20 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x30/0x180 kernel/locking/lockdep.c:6764
2 locks held by dhcpcd/5506:
 #0: ffffffff8edf61b0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1733 [inline]
 #0: ffffffff8edf61b0 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x1d6/0x22c0 kernel/fork.c:1786
 #1: ffff88805a8a3de0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:146 [inline]
 #1: ffff88805a8a3de0 (&mm->mmap_lock){++++}-{4:4}, at: dup_mmap kernel/fork.c:620 [inline]
 #1: ffff88805a8a3de0 (&mm->mmap_lock){++++}-{4:4}, at: dup_mm kernel/fork.c:1734 [inline]
 #1: ffff88805a8a3de0 (&mm->mmap_lock){++++}-{4:4}, at: copy_mm+0x2a8/0x22c0 kernel/fork.c:1786
2 locks held by getty/5594:
 #0: ffff8880319c50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x5bb/0x1700 drivers/tty/n_tty.c:2222
1 lock held by syz-executor253/8529:
 #0: ffff88807b09bde0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:128 [inline]
 #0: ffff88807b09bde0 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x305/0xde0 mm/mmap.c:1292
1 lock held by dhcpcd/8530:
 #0: ffff8880253947e0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:146 [inline]
 #0: ffff8880253947e0 (&mm->mmap_lock){++++}-{4:4}, at: __vm_munmap+0x213/0x520 mm/vma.c:3010

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.15.0-rc2-syzkaller-00258-g750d0ac001e8 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x4ab/0x4e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:274 [inline]
 watchdog+0x1058/0x10a0 kernel/hung_task.c:437
 kthread+0x7b7/0x940 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 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: 0 Comm: swapper/1 Not tainted 6.15.0-rc2-syzkaller-00258-g750d0ac001e8 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:81
Code: cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 73 8f 18 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197dc0 EFLAGS: 000002c2
RAX: 330d1d9510403d00 RBX: ffffffff8197272e RCX: ffffffff8c2fa93c
RDX: 0000000000000001 RSI: ffffffff8e6499b7 RDI: ffffffff8ca1b5a0
RBP: ffffc90000197f20 R08: ffff8880b8732b5b R09: 1ffff110170e656b
R10: dffffc0000000000 R11: ffffed10170e656c R12: 1ffff92000032fd2
R13: 1ffff11003ad9b40 R14: 0000000000000001 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff88812509a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6b30e296c0 CR3: 000000000eb38000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:748
 default_idle_call+0x74/0xb0 kernel/sched/idle.c:117
 cpuidle_idle_call kernel/sched/idle.c:185 [inline]
 do_idle+0x22e/0x5d0 kernel/sched/idle.c:325
 cpu_startup_entry+0x42/0x60 kernel/sched/idle.c:423
 start_secondary+0xfe/0x100 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x147
 </TASK>