syzbot

INFO: task syz.8.498:10221 blocked for more than 143 seconds.
      Not tainted 6.16.0-rc4-syzkaller-00123-g4c06e63b9203 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.498       state:D stack:28904 pid:10221 tgid:10188 ppid:9011   task_flags:0x400040 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5396 [inline]
 __schedule+0x16a2/0x4cb0 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
 fdget_pos+0x247/0x320 fs/file.c:1217
 class_fd_pos_constructor include/linux/file.h:85 [inline]
 ksys_read+0x79/0x250 fs/read_write.c:706
 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: 0033:0x7fc62838e929
RSP: 002b:00007fc629188038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fc6285b6160 RCX: 00007fc62838e929
RDX: 0000000000002020 RSI: 0000200000009800 RDI: 0000000000000006
RBP: 00007fc628410b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fc6285b6160 R15: 00007ffe8e415768
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e13ee20 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e13ee20 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e13ee20 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6770
5 locks held by kworker/u8:2/36:
4 locks held by kworker/u8:6/1104:
2 locks held by getty/5602:
 #0: ffff88814ceb80a0 (&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+0x43e/0x1400 drivers/tty/n_tty.c:2222
3 locks held by udevd/5857:
1 lock held by syz.8.498/10189:
 #0: ffff8880784b8428 (sb_writers#19){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3096 [inline]
 #0: ffff8880784b8428 (sb_writers#19){.+.+}-{0:0}, at: vfs_write+0x211/0xa90 fs/read_write.c:682
2 locks held by syz.8.498/10219:
 #0: ffff888030356d38 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1217
 #1: ffff8880784b8428 (sb_writers#19){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3096 [inline]
 #1: ffff8880784b8428 (sb_writers#19){.+.+}-{0:0}, at: vfs_write+0x211/0xa90 fs/read_write.c:682
1 lock held by syz.8.498/10221:
 #0: ffff888030356d38 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1217
2 locks held by syz.3.503/10492:
 #0: ffff8880784b80e0 (&type->s_umount_key#70){++++}-{4:4}, at: __super_lock fs/super.c:59 [inline]
 #0: ffff8880784b80e0 (&type->s_umount_key#70){++++}-{4:4}, at: super_lock+0x2a9/0x3b0 fs/super.c:121
 #1: ffff8880784b8950 (&s->s_sync_lock){+.+.}-{4:4}, at: wait_sb_inodes fs/fs-writeback.c:2653 [inline]
 #1: ffff8880784b8950 (&s->s_sync_lock){+.+.}-{4:4}, at: sync_inodes_sb+0x255/0xa10 fs/fs-writeback.c:2836
2 locks held by syz.8.589/11566:
 #0: ffff8880784b80e0 (&type->s_umount_key#70){++++}-{4:4}, at: __super_lock fs/super.c:59 [inline]
 #0: ffff8880784b80e0 (&type->s_umount_key#70){++++}-{4:4}, at: super_lock+0x2a9/0x3b0 fs/super.c:121
 #1: ffff8880784b8950 (&s->s_sync_lock){+.+.}-{4:4}, at: wait_sb_inodes fs/fs-writeback.c:2653 [inline]
 #1: ffff8880784b8950 (&s->s_sync_lock){+.+.}-{4:4}, at: sync_inodes_sb+0x255/0xa10 fs/fs-writeback.c:2836
1 lock held by syz.1.656/12615:
3 locks held by syz.7.653/12618:
 #0: ffff888022d818b0 (&bdev->bd_fsfreeze_mutex){+.+.}-{4:4}, at: bdev_freeze+0x2a/0x220 block/bdev.c:289
 #1: ffff88804871e428 (sb_writers#15){++++}-{0:0}, at: sb_wait_write fs/super.c:1900 [inline]
 #1: ffff88804871e428 (sb_writers#15){++++}-{0:0}, at: freeze_super+0x4db/0x1130 fs/super.c:2164
 #2: ffffffff8e144938 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:336 [inline]
 #2: ffffffff8e144938 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730 kernel/rcu/tree_exp.h:998
2 locks held by syz.7.653/12648:
1 lock held by sed/12647:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.16.0-rc4-syzkaller-00123-g4c06e63b9203 #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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 66 Comm: kworker/u8:4 Not tainted 6.16.0-rc4-syzkaller-00123-g4c06e63b9203 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:23 [inline]
RIP: 0010:raw_atomic_read include/linux/atomic/atomic-arch-fallback.h:457 [inline]
RIP: 0010:rcu_is_watching_curr_cpu include/linux/context_tracking.h:128 [inline]
RIP: 0010:rcu_is_watching+0x5a/0xb0 kernel/rcu/tree.c:745
Code: f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 0c 93 7a 00 48 c7 c3 58 1f 9e 92 49 03 1e 48 89 d8 48 c1 e8 03 42 0f b6 04 38 <84> c0 75 34 8b 03 65 ff 0d 79 cd f5 10 74 11 83 e0 04 c1 e8 02 5b
RSP: 0000:ffffc9000214fa00 EFLAGS: 00000a06
RAX: 0000000000000000 RBX: ffff8880b8732f58 RCX: 0adcfb96c931d200
RDX: ffff88801cf29e00 RSI: ffffffff8be1bc20 RDI: ffffffff8be1bbe0
RBP: ffff8880404e5410 R08: 0000000000000000 R09: ffffffff8b360122
R10: dffffc0000000000 R11: ffffffff8b360050 R12: dffffc0000000000
R13: ffffffff8b360122 R14: ffffffff8dba8c68 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888125d51000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcf5f9dd000 CR3: 0000000033e08000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rcu_read_lock include/linux/rcupdate.h:842 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 batadv_nc_worker+0x10c/0x610 net/batman-adv/network-coding.c:719
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
 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>