====================================================== WARNING: possible circular locking dependency detected 5.17.0-next-20220330-syzkaller #0 Not tainted ------------------------------------------------------ kworker/1:18/18127 is trying to acquire lock: ffff88807f294460 (sb_writers#3){.+.+}-{0:0}, at: p9_fd_write net/9p/trans_fd.c:428 [inline] ffff88807f294460 (sb_writers#3){.+.+}-{0:0}, at: p9_write_work+0x25e/0xca0 net/9p/trans_fd.c:479 but task is already holding lock: ffffc90003757da8 ((work_completion)(&m->wq)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 ((work_completion)(&m->wq)){+.+.}-{0:0}: process_one_work+0x905/0x1610 kernel/workqueue.c:2265 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 -> #2 ((wq_completion)events){+.+.}-{0:0}: flush_workqueue+0x164/0x1440 kernel/workqueue.c:2831 flush_scheduled_work include/linux/workqueue.h:583 [inline] ext4_put_super+0x99/0x1150 fs/ext4/super.c:1202 generic_shutdown_super+0x14c/0x400 fs/super.c:462 kill_block_super+0x97/0xf0 fs/super.c:1394 deactivate_locked_super+0x94/0x160 fs/super.c:332 deactivate_super+0xad/0xd0 fs/super.c:363 cleanup_mnt+0x3a2/0x540 fs/namespace.c:1186 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:183 [inline] exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:215 __syscall_exit_to_user_mode_work kernel/entry/common.c:297 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:308 do_syscall_64+0x42/0x80 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #1 (&type->s_umount_key#32){++++}-{3:3}: down_read+0x98/0x440 kernel/locking/rwsem.c:1461 iterate_supers+0xdb/0x290 fs/super.c:692 drop_caches_sysctl_handler+0xdb/0x110 fs/drop_caches.c:62 proc_sys_call_handler+0x4a1/0x6e0 fs/proc/proc_sysctl.c:604 call_write_iter include/linux/fs.h:2080 [inline] do_iter_readv_writev+0x3d1/0x640 fs/read_write.c:726 do_iter_write+0x182/0x700 fs/read_write.c:852 vfs_iter_write+0x70/0xa0 fs/read_write.c:893 iter_file_splice_write+0x723/0xc70 fs/splice.c:689 do_splice_from fs/splice.c:767 [inline] direct_splice_actor+0x110/0x180 fs/splice.c:936 splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891 do_splice_direct+0x1a7/0x270 fs/splice.c:979 do_sendfile+0xae0/0x1240 fs/read_write.c:1246 __do_sys_sendfile64 fs/read_write.c:1305 [inline] __se_sys_sendfile64 fs/read_write.c:1297 [inline] __x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1297 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (sb_writers#3){.+.+}-{0:0}: check_prev_add kernel/locking/lockdep.c:3096 [inline] check_prevs_add kernel/locking/lockdep.c:3219 [inline] validate_chain kernel/locking/lockdep.c:3834 [inline] __lock_acquire+0x2ac6/0x56c0 kernel/locking/lockdep.c:5060 lock_acquire kernel/locking/lockdep.c:5672 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5637 percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1728 [inline] sb_start_write include/linux/fs.h:1798 [inline] file_start_write include/linux/fs.h:2815 [inline] kernel_write fs/read_write.c:564 [inline] kernel_write+0x2ac/0x540 fs/read_write.c:555 p9_fd_write net/9p/trans_fd.c:428 [inline] p9_write_work+0x25e/0xca0 net/9p/trans_fd.c:479 process_one_work+0x996/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 other info that might help us debug this: Chain exists of: sb_writers#3 --> (wq_completion)events --> (work_completion)(&m->wq) Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&m->wq)); lock((wq_completion)events); lock((work_completion)(&m->wq)); lock(sb_writers#3); *** DEADLOCK *** 2 locks held by kworker/1:18/18127: #0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] #0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline] #0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:636 [inline] #0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:663 [inline] #0: ffff888010c64d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x87a/0x1610 kernel/workqueue.c:2260 #1: ffffc90003757da8 ((work_completion)(&m->wq)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264 stack backtrace: CPU: 1 PID: 18127 Comm: kworker/1:18 Not tainted 5.17.0-next-20220330-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events p9_write_work Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2176 check_prev_add kernel/locking/lockdep.c:3096 [inline] check_prevs_add kernel/locking/lockdep.c:3219 [inline] validate_chain kernel/locking/lockdep.c:3834 [inline] __lock_acquire+0x2ac6/0x56c0 kernel/locking/lockdep.c:5060 lock_acquire kernel/locking/lockdep.c:5672 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5637 percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1728 [inline] sb_start_write include/linux/fs.h:1798 [inline] file_start_write include/linux/fs.h:2815 [inline] kernel_write fs/read_write.c:564 [inline] kernel_write+0x2ac/0x540 fs/read_write.c:555 p9_fd_write net/9p/trans_fd.c:428 [inline] p9_write_work+0x25e/0xca0 net/9p/trans_fd.c:479 process_one_work+0x996/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 kernel write not supported for file task/24614/net/rt_cache (pid: 18127 comm: kworker/1:18) usb 1-1: USB disconnect, device number 32 usb 1-1: USB disconnect, device number 33