Hello, syzbot found the following issue on: HEAD commit: a90af8f15bdc Merge tag 'libata-5.16-rc2' of git://git.kern.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13df9b11b00000 kernel config: https://syzkaller.appspot.com/x/.config?x=6d3b8fd1977c1e73 dashboard link: https://syzkaller.appspot.com/bug?extid=14aea3976ea68c2c5f01 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 Unfortunately, I don't have any reproducer for this issue yet. IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+14aea3976ea68c2c5f01@xxxxxxxxxxxxxxxxxxxxxxxxx INFO: task kworker/u4:10:5840 blocked for more than 143 seconds. Not tainted 5.16.0-rc1-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u4:10 state:D stack:26616 pid: 5840 ppid: 2 flags:0x00004000 Workqueue: nbd-del nbd_dev_remove_work Call Trace: <TASK> context_switch kernel/sched/core.c:4972 [inline] __schedule+0xa9a/0x4940 kernel/sched/core.c:6253 schedule+0xd2/0x260 kernel/sched/core.c:6326 blk_mq_freeze_queue_wait+0x112/0x160 block/blk-mq.c:178 del_gendisk+0x598/0x860 block/genhd.c:623 nbd_dev_remove+0x3c/0xf0 drivers/block/nbd.c:252 process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> INFO: task kworker/u4:15:6546 blocked for more than 143 seconds. Not tainted 5.16.0-rc1-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u4:15 state:D stack:27496 pid: 6546 ppid: 2 flags:0x00004000 Workqueue: nbd-del nbd_dev_remove_work Call Trace: <TASK> context_switch kernel/sched/core.c:4972 [inline] __schedule+0xa9a/0x4940 kernel/sched/core.c:6253 schedule+0xd2/0x260 kernel/sched/core.c:6326 blk_mq_freeze_queue_wait+0x112/0x160 block/blk-mq.c:178 del_gendisk+0x598/0x860 block/genhd.c:623 nbd_dev_remove+0x3c/0xf0 drivers/block/nbd.c:252 process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> Showing all locks held in the system: 1 lock held by khungtaskd/27: #0: ffffffff8bb83b60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6458 1 lock held by in:imklog/6233: #0: ffff888022de7270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990 5 locks held by agetty/6454: 2 locks held by kworker/u4:10/5840: #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:635 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:662 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2269 #1: ffffc9000ba87db0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2273 2 locks held by kworker/u4:15/6546: #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:635 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:662 [inline] #0: ffff88801a512138 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2269 #1: ffffc90002fffdb0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2273 4 locks held by kworker/u4:16/6563: #0: ffff888011a03138 ((wq_completion)netns){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888011a03138 ((wq_completion)netns){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] #0: ffff888011a03138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline] #0: ffff888011a03138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:635 [inline] #0: ffff888011a03138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:662 [inline] #0: ffff888011a03138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2269 #1: ffffc90003127db0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2273 #2: ffffffff8d2f9290 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xb00 net/core/net_namespace.c:555 #3: ffffffff8bb8cdf0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x44/0x440 kernel/rcu/tree.c:3985 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.16.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline] watchdog+0xc1d/0xf50 kernel/hung_task.c:295 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 6454 Comm: agetty Not tainted 5.16.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:slow_down_io arch/x86/include/asm/paravirt.h:55 [inline] RIP: 0010:outb_p arch/x86/include/asm/io.h:334 [inline] RIP: 0010:vga_io_w include/video/vga.h:209 [inline] RIP: 0010:setmask drivers/video/fbdev/vga16fb.c:139 [inline] RIP: 0010:vga_8planes_imageblit drivers/video/fbdev/vga16fb.c:1141 [inline] RIP: 0010:vga_imageblit_expand drivers/video/fbdev/vga16fb.c:1203 [inline] RIP: 0010:vga16fb_imageblit+0x1c93/0x2aa0 drivers/video/fbdev/vga16fb.c:1260 Code: 5d 0c 44 89 f6 89 df e8 9b 1f 5d fd 41 39 de 0f 82 0c ff ff ff 48 8b 5c 24 58 e8 88 1c 5d fd ba cf 03 00 00 0f b6 44 24 48 ee <48> b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 80 3c 02 00 0f RSP: 0018:ffffc90001cff4c0 EFLAGS: 00000293 RAX: 00000000000000ff RBX: ffffffff8b9f7d20 RCX: 0000000000000000 RDX: 00000000000003cf RSI: ffffffff841a7cd8 RDI: 0000000000000003 RBP: ffffc90001cff650 R08: 0000000000000010 R09: 0000000000000001 R10: ffffffff841a7cc5 R11: 0000000000000001 R12: dffffc0000000000 R13: ffff8880000a144a R14: 0000000000000010 R15: ffff888017e3c000 FS: 00007f84bd17a500(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055bfa2d56160 CR3: 0000000019976000 CR4: 0000000000350ee0 Call Trace: <TASK> bit_putcs_unaligned drivers/video/fbdev/core/bitblit.c:124 [inline] bit_putcs+0x6e1/0xd20 drivers/video/fbdev/core/bitblit.c:173 fbcon_putcs+0x353/0x440 drivers/video/fbdev/core/fbcon.c:1277 fbcon_redraw.constprop.0+0x41a/0x4b0 drivers/video/fbdev/core/fbcon.c:1435 fbcon_scroll+0x45c/0x610 drivers/video/fbdev/core/fbcon.c:1469 con_scroll+0x5b9/0x6d0 drivers/tty/vt/vt.c:630 lf+0x26b/0x2c0 drivers/tty/vt/vt.c:1507 vc_con_write_normal drivers/tty/vt/vt.c:2851 [inline] do_con_write+0xf1c/0x1e40 drivers/tty/vt/vt.c:2955 con_write+0x21/0x40 drivers/tty/vt/vt.c:3295 n_tty_write+0xa7a/0xfd0 drivers/tty/n_tty.c:2311 do_tty_write drivers/tty/tty_io.c:1038 [inline] file_tty_write.constprop.0+0x526/0x910 drivers/tty/tty_io.c:1110 call_write_iter include/linux/fs.h:2162 [inline] new_sync_write+0x429/0x660 fs/read_write.c:503 vfs_write+0x7cd/0xae0 fs/read_write.c:590 ksys_write+0x12d/0x250 fs/read_write.c:643 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f84bcc97970 Code: 73 01 c3 48 8b 0d 28 d5 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 99 2d 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 7e 9b 01 00 48 89 04 24 RSP: 002b:00007ffddedd0448 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f84bcc97970 RDX: 0000000000000009 RSI: 00007ffddedd0610 RDI: 0000000000000001 RBP: 00007ffddedd0610 R08: 00007f84bd17a500 R09: 0000000000000009 R10: 0000000000000073 R11: 0000000000000246 R12: 0000000000000009 R13: 0000000000000001 R14: 00007f84bcf56600 R15: 0000000000000009 </TASK> ---------------- Code disassembly (best guess): 0: 5d pop %rbp 1: 0c 44 or $0x44,%al 3: 89 f6 mov %esi,%esi 5: 89 df mov %ebx,%edi 7: e8 9b 1f 5d fd callq 0xfd5d1fa7 c: 41 39 de cmp %ebx,%r14d f: 0f 82 0c ff ff ff jb 0xffffff21 15: 48 8b 5c 24 58 mov 0x58(%rsp),%rbx 1a: e8 88 1c 5d fd callq 0xfd5d1ca7 1f: ba cf 03 00 00 mov $0x3cf,%edx 24: 0f b6 44 24 48 movzbl 0x48(%rsp),%eax 29: ee out %al,(%dx) * 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction 31: fc ff df 34: 48 89 da mov %rbx,%rdx 37: 48 c1 ea 03 shr $0x3,%rdx 3b: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) 3f: 0f .byte 0xf --- This report is generated by a bot. 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