syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.576/8202 is trying to acquire lock:
ffff88807d2a00e0 (&type->s_umount_key#31){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
ffff88807d2a00e0 (&type->s_umount_key#31){++++}-{3:3}, at: super_lock+0x167/0x360 fs/super.c:117

but task is already holding lock:
ffff88801fe6c608 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: bdev_mark_dead+0x31/0x1a0 block/bdev.c:1011

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&bdev->bd_holder_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       bd_finish_claiming+0x22f/0x3f0 block/bdev.c:568
       blkdev_get_by_dev+0x45c/0x600 block/bdev.c:801
       bdev_open_by_dev+0x77/0x100 block/bdev.c:842
       setup_bdev_super+0x59/0x660 fs/super.c:1496
       mount_bdev+0x1dd/0x2d0 fs/super.c:1640
       legacy_get_tree+0xea/0x180 fs/fs_context.c:662
       vfs_get_tree+0x8c/0x280 fs/super.c:1764
       do_new_mount+0x24b/0xa40 fs/namespace.c:3377
       init_mount+0xd2/0x120 fs/init.c:25
       do_mount_root+0x97/0x230 init/do_mounts.c:166
       mount_root_generic+0x195/0x3c0 init/do_mounts.c:205
       prepare_namespace+0xc2/0x100 init/do_mounts.c:489
       kernel_init_freeable+0x413/0x570 init/main.c:1566
       kernel_init+0x1d/0x1c0 init/main.c:1443
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

-> #3 (bdev_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       bd_prepare_to_claim+0x1ba/0x480 block/bdev.c:510
       truncate_bdev_range+0x4e/0x260 block/bdev.c:105
       blk_ioctl_discard block/ioctl.c:118 [inline]
       blkdev_common_ioctl+0x1efe/0x23d0 block/ioctl.c:509
       blkdev_ioctl+0x4eb/0x6f0 block/ioctl.c:627
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:871 [inline]
       __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (mapping.invalidate_lock#2){++++}-{3:3}:
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       filemap_invalidate_lock_shared include/linux/fs.h:859 [inline]
       page_cache_ra_unbounded+0xdc/0x770 mm/readahead.c:225
       page_cache_sync_readahead include/linux/pagemap.h:1325 [inline]
       ext4_readdir+0xb71/0x39d0 fs/ext4/dir.c:197
       iterate_dir+0x1c2/0x580 fs/readdir.c:106
       __do_sys_getdents64 fs/readdir.c:405 [inline]
       __se_sys_getdents64+0xe9/0x260 fs/readdir.c:390
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&type->i_mutex_dir_key#3){++++}-{3:3}:
       down_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
       inode_lock include/linux/fs.h:804 [inline]
       ext4_process_orphan+0x187/0x300 fs/ext4/orphan.c:337
       ext4_orphan_cleanup+0xbd4/0x1400 fs/ext4/orphan.c:474
       __ext4_fill_super fs/ext4/super.c:5608 [inline]
       ext4_fill_super+0x5de7/0x66c0 fs/ext4/super.c:5731
       get_tree_bdev+0x3e4/0x510 fs/super.c:1591
       vfs_get_tree+0x8c/0x280 fs/super.c:1764
       do_new_mount+0x24b/0xa40 fs/namespace.c:3377
       do_mount fs/namespace.c:3717 [inline]
       __do_sys_mount fs/namespace.c:3926 [inline]
       __se_sys_mount+0x2da/0x3c0 fs/namespace.c:3903
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&type->s_umount_key#31){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
       lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
       __super_lock fs/super.c:58 [inline]
       super_lock+0x167/0x360 fs/super.c:117
       super_lock_shared fs/super.c:146 [inline]
       super_lock_shared_active fs/super.c:1442 [inline]
       fs_bdev_mark_dead+0xad/0x1f0 fs/super.c:1458
       bdev_mark_dead+0x83/0x1a0 block/bdev.c:1013
       disk_force_media_change+0x132/0x1b0 block/disk-events.c:302
       __loop_clr_fd+0x396/0x660 drivers/block/loop.c:1170
       loop_clr_fd drivers/block/loop.c:1253 [inline]
       lo_ioctl+0x11e8/0x19f0 drivers/block/loop.c:1578
       blkdev_ioctl+0x58b/0x6f0 block/ioctl.c:633
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:871 [inline]
       __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  &type->s_umount_key#31 --> bdev_lock --> &bdev->bd_holder_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&bdev->bd_holder_lock);
                               lock(bdev_lock);
                               lock(&bdev->bd_holder_lock);
  rlock(&type->s_umount_key#31);

 *** DEADLOCK ***

1 lock held by syz.2.576/8202:
 #0: ffff88801fe6c608 (&bdev->bd_holder_lock){+.+.}-{3:3}, at: bdev_mark_dead+0x31/0x1a0 block/bdev.c:1011

stack backtrace:
CPU: 0 PID: 8202 Comm: syz.2.576 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_noncircular+0x2bd/0x3c0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
 __super_lock fs/super.c:58 [inline]
 super_lock+0x167/0x360 fs/super.c:117
 super_lock_shared fs/super.c:146 [inline]
 super_lock_shared_active fs/super.c:1442 [inline]
 fs_bdev_mark_dead+0xad/0x1f0 fs/super.c:1458
 bdev_mark_dead+0x83/0x1a0 block/bdev.c:1013
 disk_force_media_change+0x132/0x1b0 block/disk-events.c:302
 __loop_clr_fd+0x396/0x660 drivers/block/loop.c:1170
 loop_clr_fd drivers/block/loop.c:1253 [inline]
 lo_ioctl+0x11e8/0x19f0 drivers/block/loop.c:1578
 blkdev_ioctl+0x58b/0x6f0 block/ioctl.c:633
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb87d98e7ab
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007fb87e829dc0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007fb87d98e7ab
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000006
RBP: 0000000000000010 R08: 0000000000000000 R09: 000000000000056b
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: 00007fb87e829ef0 R14: 00007fb87e82a668 R15: 00007fb8737f7000
 </TASK>
loop2: detected capacity change from 0 to 512
EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /168/bus supports timestamps until 2038-01-19 (0x7fffffff)