====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ udevd/4181 is trying to acquire lock: ffff8880641e2d38 (&iint_mutex_key[depth]){+.+.}-{3:3}, at: process_measurement+0x724/0x1c20 security/integrity/ima/ima_main.c:261 but task is already holding lock: ffff88807e6e6460 (sb_writers#3){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:386 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)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 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: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 -> #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 blkdev_get_by_dev+0x162/0xa50 block/bdev.c:816 blkdev_get_by_path+0x1b8/0x2e0 block/bdev.c:887 register_bcache+0x15e/0x6150 drivers/md/bcache/super.c:2584 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_file_read_iter fs/kernfs/file.c:203 [inline] kernfs_fop_read_iter+0x185/0x560 fs/kernfs/file.c:242 __kernel_read+0x51d/0x980 fs/read_write.c:443 integrity_kernel_read+0x86/0xd0 security/integrity/iint.c:228 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline] ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline] ima_calc_file_hash+0x946/0x1940 security/integrity/ima/ima_crypto.c:573 ima_collect_measurement+0x335/0x7e0 security/integrity/ima/ima_api.c:255 process_measurement+0x1185/0x1c20 security/integrity/ima/ima_main.c:351 ima_file_check+0xc7/0x110 security/integrity/ima/ima_main.c:533 do_open fs/namei.c:3661 [inline] path_openat+0x27cf/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 (&iint_mutex_key[depth]){+.+.}-{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 process_measurement+0x724/0x1c20 security/integrity/ima/ima_main.c:261 ima_file_check+0xc7/0x110 security/integrity/ima/ima_main.c:533 do_open fs/namei.c:3661 [inline] path_openat+0x27cf/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 other info that might help us debug this: Chain exists of: &iint_mutex_key[depth] --> (work_completion)(&lo->rootcg_work) --> sb_writers#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(sb_writers#3); lock((work_completion)(&lo->rootcg_work)); lock(sb_writers#3); lock(&iint_mutex_key[depth]); *** DEADLOCK *** 1 lock held by udevd/4181: #0: ffff88807e6e6460 (sb_writers#3){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:386 stack backtrace: CPU: 0 PID: 4181 Comm: udevd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 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 process_measurement+0x724/0x1c20 security/integrity/ima/ima_main.c:261 ima_file_check+0xc7/0x110 security/integrity/ima/ima_main.c:533 do_open fs/namei.c:3661 [inline] path_openat+0x27cf/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 RIP: 0033:0x7fdfe2db4407 Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007fff3de706f0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007fdfe2cc6880 RCX: 00007fdfe2db4407 RDX: 00000000000a0241 RSI: 00007fff3de713b0 RDI: ffffffffffffff9c RBP: 000055fcbf5d8e40 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000124 R11: 0000000000000202 R12: 000055fcbf5ca340 R13: 00007fff3de713b0 R14: 00007fff3de70fb0 R15: 00007fff3de70bb0