INFO: task syz-executor.1:3021 blocked for more than 140 seconds. Not tainted 4.14.198-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D28912 3021 6378 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3384 schedule+0x8d/0x1b0 kernel/sched/core.c:3428 schedule_timeout+0x80a/0xe90 kernel/time/timer.c:1731 do_wait_for_common kernel/sched/completion.c:91 [inline] __wait_for_common kernel/sched/completion.c:112 [inline] wait_for_common+0x272/0x430 kernel/sched/completion.c:123 ucma_close+0xfc/0x340 drivers/infiniband/core/ucma.c:1749 __fput+0x25f/0x7a0 fs/file_table.c:210 task_work_run+0x11f/0x190 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x417901 RSP: 002b:00007ffcc7ab4550 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000417901 RDX: 0000001b31f20000 RSI: 000000000000086e RDI: 0000000000000003 RBP: 0000000000000001 R08: 00000000216a486e R09: 00000000216a4872 R10: 00007ffcc7ab4640 R11: 0000000000000293 R12: 00000000011905d8 R13: 000000000006f241 R14: ffffffffffffffff R15: 000000000118cf4c Showing all locks held in the system: 1 lock held by khungtaskd/1068: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548 2 locks held by agetty/6068: #0: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e3/0x1680 drivers/tty/n_tty.c:2156 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1068 Comm: khungtaskd Not tainted 4.14.198-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x283 lib/dump_stack.c:58 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x13a/0x17f lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x5b9/0xb40 kernel/hung_task.c:274 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 2343 Comm: kworker/u4:4 Not tainted 4.14.198-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: phy15 ieee80211_iface_work task: ffff8880a1610500 task.stack: ffff8880a1618000 RIP: 0010:memcmp+0x3e/0xb0 lib/string.c:861 RSP: 0000:ffff8880a161f9d8 EFLAGS: 00000002 RAX: 0000000000000000 RBX: ffff8880a161fa82 RCX: 0000000000000001 RDX: 0000000000000002 RSI: ffff8880a41fc1da RDI: ffff8880a161fa70 RBP: dffffc0000000000 R08: ffffffff8951e65e R09: ffffffff8951e762 R10: 000000000011e148 R11: 0000000000058071 R12: ffff8880a161fab8 R13: 0000000000000009 R14: ffff8880a161fa70 R15: ffff8880a41fc1b0 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8d90c21000 CR3: 00000000a7eee000 CR4: 00000000001426e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: find_stack lib/stackdepot.c:180 [inline] depot_save_stack+0x10d/0x3e3 lib/stackdepot.c:229 save_stack mm/kasan/kasan.c:453 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x117/0x1a0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758 kfree_skbmem+0x98/0x100 net/core/skbuff.c:586 __kfree_skb net/core/skbuff.c:646 [inline] kfree_skb+0xf4/0x390 net/core/skbuff.c:663 ieee80211_iface_work+0x1d7/0x770 net/mac80211/iface.c:1374 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: fc ff df 53 48 89 fb 48 83 ec 10 eb 0d 48 83 c3 01 48 83 c6 01 49 39 dc 74 45 48 89 d8 48 89 da 48 c1 e8 03 83 e2 07 0f b6 04 28 <38> d0 7f 04 84 c0 75 54 48 89 f2 48 89 f1 0f b6 03 48 c1 ea 03