====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.4.553/6366 is trying to acquire lock: ffff88805ad13068 (&pipe->mutex/1){+.+.}-{3:3}, at: iter_file_splice_write+0x1b6/0xcf0 fs/splice.c:635 but task is already holding lock: ffff88807d84a460 (sb_writers#3){.+.+}-{0:0}, at: __do_splice fs/splice.c:1173 [inline] (sb_writers#3){.+.+}-{0:0}, at: __do_sys_splice fs/splice.c:1379 [inline] (sb_writers#3){.+.+}-{0:0}, at: __se_sys_splice+0x34d/0x440 fs/splice.c:1361 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #9 (sb_writers#3){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1817 [inline] sb_start_write include/linux/fs.h:1887 [inline] file_start_write include/linux/fs.h:3054 [inline] lo_write_bvec+0x194/0x780 drivers/block/loop.c:315 lo_write_simple drivers/block/loop.c:338 [inline] do_req_filebacked drivers/block/loop.c:656 [inline] loop_handle_cmd drivers/block/loop.c:2235 [inline] loop_process_work+0x1b66/0x24c0 drivers/block/loop.c:2275 process_one_work+0x867/0xff0 kernel/workqueue.c:2310 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457 kthread+0x42e/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #8 ((work_completion)(&worker->work)){+.+.}-{0:0}: process_one_work+0x7ba/0xff0 kernel/workqueue.c:2286 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457 kthread+0x42e/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #7 ((wq_completion)loop4){+.+.}-{0:0} : flush_workqueue+0x16a/0x1390 kernel/workqueue.c:2830 drain_workqueue+0xca/0x370 kernel/workqueue.c:2995 destroy_workqueue+0x7b/0xb20 kernel/workqueue.c:4439 __loop_clr_fd+0x22f/0xb50 drivers/block/loop.c:1384 blkdev_put+0x52b/0x780 block/bdev.c:-1 blkdev_close+0x76/0xa0 block/fops.c:478 __fput+0x212/0x8c0 fs/file_table.c:311 task_work_run+0x125/0x1a0 kernel/task_work.c:188 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:184 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:217 __syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:310 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #6 (&lo->lo_mutex){+.+.}-{3:3} : __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_killable_nested+0x17/0x20 kernel/locking/mutex.c:758 lo_open+0x6a/0x100 drivers/block/loop.c:2056 blkdev_get_whole+0x90/0x390 block/bdev.c:665 blkdev_get_by_dev+0x2da/0xa50 block/bdev.c:823 blkdev_open+0x128/0x2c0 block/fops.c:466 do_dentry_open+0x7f7/0xf90 fs/open.c:826 do_open fs/namei.c:3659 [inline] path_openat+0x2718/0x2fb0 fs/namei.c:3793 do_filp_open+0x1df/0x400 fs/namei.c:3820 do_sys_openat2+0x14b/0x500 fs/open.c:1255 do_sys_open fs/open.c:1271 [inline] __do_sys_openat fs/open.c:1287 [inline] __se_sys_openat fs/open.c:1282 [inline] __x64_sys_openat+0x135/0x160 fs/open.c:1282 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #5 (&disk->open_mutex){+.+.}-{3:3}: __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 bd_register_pending_holders+0x33/0x310 block/holder.c:161 device_add_disk+0x5ee/0xde0 block/genhd.c:493 add_disk include/linux/genhd.h:200 [inline] md_alloc+0x80e/0xc10 drivers/md/md.c:5789 add_named_array+0x1bd/0x290 drivers/md/md.c:-1 param_attr_store+0x20a/0x300 kernel/params.c:585 module_attr_store+0x5b/0x80 kernel/params.c:905 kernfs_fop_write_iter+0x3a8/0x500 fs/kernfs/file.c:296 call_write_iter include/linux/fs.h:2179 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x748/0xd70 fs/read_write.c:594 ksys_write+0x153/0x260 fs/read_write.c:647 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #4 (disks_mutex){+.+.}-{3:3}: __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 md_alloc+0x48/0xc10 drivers/md/md.c:5730 add_named_array+0x1bd/0x290 drivers/md/md.c:-1 param_attr_store+0x20a/0x300 kernel/params.c:585 module_attr_store+0x5b/0x80 kernel/params.c:905 kernfs_fop_write_iter+0x3a8/0x500 fs/kernfs/file.c:296 call_write_iter include/linux/fs.h:2179 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x748/0xd70 fs/read_write.c:594 ksys_write+0x153/0x260 fs/read_write.c:647 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #3 (param_lock){+.+.}-{3:3} : __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 ieee80211_rate_control_ops_get net/mac80211/rate.c:192 [inline] rate_control_alloc net/mac80211/rate.c:239 [inline] ieee80211_init_rate_ctrl_alg+0x171/0x5e0 net/mac80211/rate.c:983 ieee80211_register_hw+0x23c6/0x3a60 net/mac80211/main.c:1252 mac80211_hwsim_new_radio+0x209d/0x4050 drivers/net/wireless/mac80211_hwsim.c:3373 init_mac80211_hwsim+0x581/0x720 drivers/net/wireless/mac80211_hwsim.c:4607 do_one_initcall+0x272/0x730 init/main.c:1276 do_initcall_level+0x13d/0x1f0 init/main.c:1349 do_initcalls+0x4b/0x90 init/main.c:1365 kernel_init_freeable+0x3d5/0x560 init/main.c:1589 kernel_init+0x19/0x1b0 init/main.c:1480 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #2 (rtnl_mutex){+.+.}-{3:3}: __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 nl80211_pre_doit+0x28/0x540 net/wireless/nl80211.c:14971 genl_family_rcv_msg_doit net/netlink/genetlink.c:726 [inline] genl_family_rcv_msg net/netlink/genetlink.c:775 [inline] genl_rcv_msg+0xccc/0xfa0 net/netlink/genetlink.c:792 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2519 genl_rcv+0x24/0x40 net/netlink/genetlink.c:803 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:706 [inline] __sock_sendmsg net/socket.c:718 [inline] ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2500 __sys_sendmsg net/socket.c:2529 [inline] __do_sys_sendmsg net/socket.c:2538 [inline] __se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #1 (cb_lock){++++}-{3:3}: down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498 genl_rcv+0x15/0x40 net/netlink/genetlink.c:802 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:706 [inline] __sock_sendmsg net/socket.c:718 [inline] sock_sendmsg net/socket.c:741 [inline] kernel_sendmsg+0x23e/0x350 net/socket.c:765 sock_no_sendpage+0x12a/0x1a0 net/core/sock.c:3044 kernel_sendpage+0x2cc/0x380 net/socket.c:3549 sock_sendpage+0x7a/0xb0 net/socket.c:1028 pipe_to_sendpage+0x22f/0x320 fs/splice.c:364 splice_from_pipe_feed fs/splice.c:418 [inline] __splice_from_pipe+0x333/0x8e0 fs/splice.c:562 splice_from_pipe fs/splice.c:597 [inline] generic_splice_sendpage+0x111/0x180 fs/splice.c:746 do_splice_from fs/splice.c:767 [inline] do_splice+0xe51/0x1620 fs/splice.c:1108 __do_splice fs/splice.c:1173 [inline] __do_sys_splice fs/splice.c:1379 [inline] __se_sys_splice+0x34d/0x440 fs/splice.c:1361 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #0 ( &pipe->mutex/1 ){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3120 [inline] check_prevs_add kernel/locking/lockdep.c:3239 [inline] validate_chain kernel/locking/lockdep.c:3855 [inline] __lock_acquire+0x38f7/0x7d40 kernel/locking/lockdep.c:5120 lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737 __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 iter_file_splice_write+0x1b6/0xcf0 fs/splice.c:635 do_splice_from fs/splice.c:767 [inline] do_splice+0xe51/0x1620 fs/splice.c:1108 __do_splice fs/splice.c:1173 [inline] __do_sys_splice fs/splice.c:1379 [inline] __se_sys_splice+0x34d/0x440 fs/splice.c:1361 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 other info that might help us debug this: Chain exists of: &pipe->mutex/1 --> (work_completion)(&worker->work) --> sb_writers#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(sb_writers#3 ); lock((work_completion)(&worker->work)); lock(sb_writers#3 ); lock(&pipe->mutex/1); *** DEADLOCK *** 1 lock held by syz.4.553/6366: #0: ffff88807d84a460 (sb_writers#3){.+.+}-{0:0}, at: __do_splice fs/splice.c:1173 [inline] (sb_writers#3){.+.+}-{0:0}, at: __do_sys_splice fs/splice.c:1379 [inline] (sb_writers#3){.+.+}-{0:0}, at: __se_sys_splice+0x34d/0x440 fs/splice.c:1361 stack backtrace: CPU: 1 PID: 6366 Comm: syz.4.553 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 check_noncircular+0x2f8/0x400 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3120 [inline] check_prevs_add kernel/locking/lockdep.c:3239 [inline] validate_chain kernel/locking/lockdep.c:3855 [inline] __lock_acquire+0x38f7/0x7d40 kernel/locking/lockdep.c:5120 lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737 __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 iter_file_splice_write+0x1b6/0xcf0 fs/splice.c:635 do_splice_from fs/splice.c:767 [inline] do_splice+0xe51/0x1620 fs/splice.c:1108 __do_splice fs/splice.c:1173 [inline] __do_sys_splice fs/splice.c:1379 [inline] __se_sys_splice+0x34d/0x440 fs/splice.c:1361 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f6431c8b1d9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f642fee3028 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 00007f6431f12fa0 RCX: 00007f6431c8b1d9 RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007f6431d22888 R08: 00402000784853bb R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f6431f13038 R14: 00007f6431f12fa0 R15: 00007ffcc6d1bf38 kcov: kcov_task_exit: t = ffff88802c161dc0, kcov->t = ffff88802c161dc0