======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.2809/12449 is trying to acquire lock:
ffff888066a8b8b8 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0x9d/0xc50 fs/seq_file.c:182

but task is already holding lock:
ffff88807a0a8460 (sb_writers#3){.+.+}-{0:0}, at: do_sendfile+0x4ff/0xe30 fs/read_write.c:1248

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #6 (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

-> #5 ((work_completion)(&lo->rootcg_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

-> #4 ((wq_completion)loop6){+.+.}-{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
       deactivate_locked_super+0x93/0xf0 fs/super.c:335
       cleanup_mnt+0x426/0x4d0 fs/namespace.c:1148
       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:181
       exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
       __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
       syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
       do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #3 (&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

-> #2 (&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
       reset_store+0x17e/0x3c0 drivers/block/zram/zram_drv.c:1790
       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

-> #1 (&of->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
       kernfs_seq_start+0x55/0x3c0 fs/kernfs/file.c:112
       seq_read_iter+0x387/0xc50 fs/seq_file.c:225
       call_read_iter include/linux/fs.h:2173 [inline]
       new_sync_read fs/read_write.c:404 [inline]
       vfs_read+0x75e/0xd50 fs/read_write.c:485
       ksys_read+0x153/0x260 fs/read_write.c:623
       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 (&p->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       __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
       seq_read_iter+0x9d/0xc50 fs/seq_file.c:182
       call_read_iter include/linux/fs.h:2173 [inline]
       generic_file_splice_read+0x3ed/0x5f0 fs/splice.c:311
       do_splice_to fs/splice.c:807 [inline]
       splice_direct_to_actor+0x41f/0xc00 fs/splice.c:881
       do_splice_direct+0x1d4/0x2f0 fs/splice.c:1008
       do_sendfile+0x524/0xe30 fs/read_write.c:1249
       __do_sys_sendfile64 fs/read_write.c:1317 [inline]
       __se_sys_sendfile64+0x141/0x1a0 fs/read_write.c:1303
       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:
  &p->lock --> (work_completion)(&lo->rootcg_work) --> sb_writers#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#3);
                               lock((work_completion)(&lo->rootcg_work));
                               lock(sb_writers#3);
  lock(&p->lock);

 *** DEADLOCK ***

1 lock held by syz.1.2809/12449:
 #0: ffff88807a0a8460 (sb_writers#3){.+.+}-{0:0}, at: do_sendfile+0x4ff/0xe30 fs/read_write.c:1248

stack backtrace:
CPU: 0 PID: 12449 Comm: syz.1.2809 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 __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
 seq_read_iter+0x9d/0xc50 fs/seq_file.c:182
 call_read_iter include/linux/fs.h:2173 [inline]
 generic_file_splice_read+0x3ed/0x5f0 fs/splice.c:311
 do_splice_to fs/splice.c:807 [inline]
 splice_direct_to_actor+0x41f/0xc00 fs/splice.c:881
 do_splice_direct+0x1d4/0x2f0 fs/splice.c:1008
 do_sendfile+0x524/0xe30 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1317 [inline]
 __se_sys_sendfile64+0x141/0x1a0 fs/read_write.c:1303
 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: 0033:0x7efe6dafd0d9
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:00007efe6bd55028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007efe6dd84fa0 RCX: 00007efe6dafd0d9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000003
RBP: 00007efe6db94024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efe6dd85038 R14: 00007efe6dd84fa0 R15: 00007fffc0b993d8
 </TASK>