====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.7.5649/21875 is trying to acquire lock: ffff8881477fc118 (&disk->open_mutex){+.+.}-{3:3}, at: reset_store+0x17e/0x3c0 drivers/block/zram/zram_drv.c:1790 but task is already holding lock: ffff88801cc9ac88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x500 fs/kernfs/file.c:287 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&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 -> #4 (&p->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 seq_read_iter+0x9d/0xc50 fs/seq_file.c:182 do_iter_readv_writev+0x47d/0x5f0 fs/read_write.c:-1 do_iter_read+0x201/0x7c0 fs/read_write.c:790 lo_read_simple drivers/block/loop.c:392 [inline] do_req_filebacked drivers/block/loop.c:663 [inline] loop_handle_cmd drivers/block/loop.c:2235 [inline] loop_process_work+0x16fd/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 -> #3 ((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 -> #2 ((wq_completion)loop7){+.+.}-{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 -> #1 (&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 -> #0 (&disk->open_mutex){+.+.}-{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 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 other info that might help us debug this: Chain exists of: &disk->open_mutex --> &p->lock --> &of->mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&of->mutex); lock(&p->lock); lock(&of->mutex); lock(&disk->open_mutex); *** DEADLOCK *** 4 locks held by syz.7.5649/21875: #0: ffff888078e15770 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056 #1: ffff88802c576460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590 #2: ffff88801cc9ac88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x500 fs/kernfs/file.c:287 #3: ffff8881479fae88 (kn->active#926){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1fd/0x500 fs/kernfs/file.c:288 stack backtrace: CPU: 1 PID: 21875 Comm: syz.7.5649 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 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 RIP: 0033:0x7f4d61c402d9 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:00007f4d5fe98028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f4d61ec7fa0 RCX: 00007f4d61c402d9 RDX: 0000000000000001 RSI: 0000200000000180 RDI: 0000000000000003 RBP: 00007f4d61cd7888 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f4d61ec8038 R14: 00007f4d61ec7fa0 R15: 00007ffdb4b74778