Hello, syzbot found the following issue on: HEAD commit: a67ba3cf9551 Add linux-next specific files for 20220330 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1636ed53700000 kernel config: https://syzkaller.appspot.com/x/.config?x=994543c31e941639 dashboard link: https://syzkaller.appspot.com/bug?extid=2289e1c10dde387e671e 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+2289e1c10dde387e671e@xxxxxxxxxxxxxxxxxxxxxxxxx ====================================================== WARNING: possible circular locking dependency detected 5.17.0-next-20220330-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/1465 is trying to acquire lock: ffff88807f0520e0 (&type->s_umount_key#32){++++}-{3:3}, at: iterate_supers+0xdb/0x290 fs/super.c:692 but task is already holding lock: ffff88807f344460 (sb_writers#3){.+.+}-{0:0}, at: __do_sys_sendfile64 fs/read_write.c:1305 [inline] ffff88807f344460 (sb_writers#3){.+.+}-{0:0}, at: __se_sys_sendfile64 fs/read_write.c:1297 [inline] ffff88807f344460 (sb_writers#3){.+.+}-{0:0}, at: __x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1297 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (sb_writers#3){.+.+}-{0:0}: 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 -> #2 ((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 -> #1 ((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 -> #0 (&type->s_umount_key#32){++++}-{3:3}: 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 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 other info that might help us debug this: Chain exists of: &type->s_umount_key#32 --> (work_completion)(&m->wq) --> sb_writers#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sb_writers#3); lock((work_completion)(&m->wq)); lock(sb_writers#3); lock(&type->s_umount_key#32); *** DEADLOCK *** 1 lock held by syz-executor.2/1465: #0: ffff88807f344460 (sb_writers#3){.+.+}-{0:0}, at: __do_sys_sendfile64 fs/read_write.c:1305 [inline] #0: ffff88807f344460 (sb_writers#3){.+.+}-{0:0}, at: __se_sys_sendfile64 fs/read_write.c:1297 [inline] #0: ffff88807f344460 (sb_writers#3){.+.+}-{0:0}, at: __x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1297 stack backtrace: CPU: 1 PID: 1465 Comm: syz-executor.2 Not tainted 5.17.0-next-20220330-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 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 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 RIP: 0033:0x7f88f7889049 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f88f89e1168 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f88f799bf60 RCX: 00007f88f7889049 RDX: 00000000200000c0 RSI: 0000000000000003 RDI: 0000000000000004 RBP: 00007f88f78e308d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000262 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc47da187f R14: 00007f88f89e1300 R15: 0000000000022000 </TASK> syz-executor.2 (1465): drop_caches: 1 --- This report is generated by a bot. 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