syzbot

INFO: task syz.4.492:7912 blocked for more than 143 seconds.
      Not tainted 6.15.0-syzkaller-13743-g8630c59e9936 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.492       state:D stack:25672 pid:7912  tgid:7911  ppid:5834   task_flags:0x400140 flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5396 [inline]
 __schedule+0x16f5/0x4d00 kernel/sched/core.c:6785
 __schedule_loop kernel/sched/core.c:6863 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6878
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6935
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x724/0xe80 kernel/locking/mutex.c:747
 sync_bdevs+0x1ac/0x340 block/bdev.c:1288
 ksys_sync+0xb9/0x150 fs/sync.c:105
 __ia32_sys_sync+0xe/0x20 fs/sync.c:113
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc9d9f8e929
RSP: 002b:00007fc9dae43038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fc9da1b5fa0 RCX: 00007fc9d9f8e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fc9da1b5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fc9da1b5fa0 R15: 00007ffeadf455a8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e13f060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e13f060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e13f060 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6770
2 locks held by getty/5589:
 #0: ffff88803084f0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
3 locks held by udevd/5848:
1 lock held by udevd/5851:
1 lock held by udevd/5855:
 #0: ffff888025353358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30 block/bdev.c:945
5 locks held by kworker/0:7/5975:
1 lock held by syz.4.492/7912:
 #0: ffff888025353358 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x1ac/0x340 block/bdev.c:1288
1 lock held by syz-executor/8038:
5 locks held by kworker/u8:15/8299:
2 locks held by syz.0.766/8995:
 #0: ffff88807bfa80e0 (&type->s_umount_key#50/1){+.+.}-{4:4}, at: alloc_super+0x204/0x970 fs/super.c:345
 #1: ffff8880b863b918 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:606

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.15.0-syzkaller-13743-g8630c59e9936 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:307 [inline]
 watchdog+0xfee/0x1030 kernel/hung_task.c:470
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5851 Comm: udevd Not tainted 6.15.0-syzkaller-13743-g8630c59e9936 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:next_tid mm/slub.c:3007 [inline]
RIP: 0010:__update_cpu_freelist_fast mm/slub.c:3604 [inline]
RIP: 0010:__slab_alloc_node mm/slub.c:4042 [inline]
RIP: 0010:slab_alloc_node mm/slub.c:4185 [inline]
RIP: 0010:kmem_cache_alloc_noprof+0xef/0x3c0 mm/slub.c:4204
Code: 00 00 41 83 fc ff 74 1a 48 8b 03 48 83 f8 ff 0f 84 d3 02 00 00 48 c1 e8 3a 41 39 c4 0f 85 5d 01 00 00 41 8b 46 28 4a 8b 1c 28 <49> 8d 4f 08 49 8b 36 4c 89 e8 4c 89 fa 65 48 0f c7 0e 74 5c eb 95
RSP: 0018:ffffc900035b7b70 EFLAGS: 00000246
RAX: 0000000000000028 RBX: ffff888077a895b0 RCX: ffffffff929f0190
RDX: 0000000000000000 RSI: 0000000000000050 RDI: ffffffff8e261960
RBP: 0000000000000d40 R08: 0000000000000000 R09: ffffffff82168bcd
R10: dffffc0000000000 R11: ffffed1004e4d378 R12: 00000000ffffffff
R13: ffff888077a89150 R14: ffff88814040b280 R15: 0000000000030740
FS:  00007f9f88392880(0000) GS:ffff888125c52000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9f88369000 CR3: 00000000576e0000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 lsm_inode_alloc security/security.c:755 [inline]
 security_inode_alloc+0x39/0x330 security/security.c:1697
 inode_init_always_gfp+0x9ed/0xdc0 fs/inode.c:306
 inode_init_always include/linux/fs.h:3277 [inline]
 alloc_inode+0x82/0x1b0 fs/inode.c:353
 new_inode+0x22/0x170 fs/inode.c:1145
 __shmem_get_inode mm/shmem.c:3045 [inline]
 shmem_get_inode+0x346/0xe90 mm/shmem.c:3119
 shmem_symlink+0xa3/0x510 mm/shmem.c:4093
 vfs_symlink+0x143/0x2f0 fs/namei.c:4730
 do_symlinkat+0x1b1/0x3f0 fs/namei.c:4756
 __do_sys_symlink fs/namei.c:4777 [inline]
 __se_sys_symlink fs/namei.c:4775 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4775
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9f87d15527
Code: f0 ff ff 77 06 c3 0f 1f 44 00 00 48 8b 15 c9 b8 0d 00 f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 b8 58 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 a1 b8 0d 00 f7 d8 64 89 02 b8
RSP: 002b:00007fff60171d08 EFLAGS: 00000206 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 0000562667a8adf0 RCX: 00007f9f87d15527
RDX: fffffffffffffe68 RSI: 00007fff60171d10 RDI: 0000562667a83490
RBP: 000000000000062d R08: 0000000000000064 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fff60171d10
R13: 0000562667a8f3e0 R14: 0000000000000008 R15: 0000562667a8adf0
 </TASK>