syzbot


possible deadlock in loop_control_ioctl

Status: upstream: reported on 2022/12/12 14:37
Reported-by: syzbot+d0cf1bafe94b60a4bf7d@syzkaller.appspotmail.com
First crash: 725d, last: 700d

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
4.19.211-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/24902 is trying to acquire lock:
00000000a2c4ed45 ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: __flush_work+0x51a/0x8b0 kernel/workqueue.c:2932

but task is already holding lock:
00000000c499225b (loop_ctl_mutex){+.+.}, at: loop_control_ioctl+0x7b/0x480 drivers/block/loop.c:2137

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (loop_ctl_mutex){+.+.}:
       lo_open+0x19/0xd0 drivers/block/loop.c:1771
       __blkdev_get+0x372/0x1480 fs/block_dev.c:1494
       blkdev_get+0xb0/0x940 fs/block_dev.c:1627
       blkdev_open+0x202/0x290 fs/block_dev.c:1788
       do_dentry_open+0x4aa/0x1160 fs/open.c:796
       do_last fs/namei.c:3421 [inline]
       path_openat+0x793/0x2df0 fs/namei.c:3537
       do_filp_open+0x18c/0x3f0 fs/namei.c:3567
       do_sys_open+0x3b3/0x520 fs/open.c:1085
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #7 (&bdev->bd_mutex){+.+.}:
       blkdev_put+0x30/0x520 fs/block_dev.c:1839
       btrfs_close_bdev fs/btrfs/volumes.c:1033 [inline]
       btrfs_close_one_device fs/btrfs/volumes.c:1057 [inline]
       close_fs_devices.part.0+0x24d/0x8e0 fs/btrfs/volumes.c:1085
       close_fs_devices fs/btrfs/volumes.c:1117 [inline]
       btrfs_close_devices+0x95/0x1f0 fs/btrfs/volumes.c:1103
       close_ctree+0x3c8/0x850 fs/btrfs/disk-io.c:4047
IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready
       generic_shutdown_super+0x144/0x370 fs/super.c:456
       kill_anon_super+0x36/0x60 fs/super.c:1032
       btrfs_kill_super+0x49/0x550 fs/btrfs/super.c:2221
       deactivate_locked_super+0x94/0x160 fs/super.c:329
       deactivate_super+0x174/0x1a0 fs/super.c:360
       cleanup_mnt+0x1a8/0x290 fs/namespace.c:1098
       task_work_run+0x148/0x1c0 kernel/task_work.c:113
IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready
       tracehook_notify_resume include/linux/tracehook.h:193 [inline]
       exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
       prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
       syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
       do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #6 (&fs_devs->device_list_mutex){+.+.}:
       btrfs_run_dev_stats+0xbb/0xa80 fs/btrfs/volumes.c:7111
       commit_cowonly_roots+0x1ce/0xc30 fs/btrfs/transaction.c:1172
       btrfs_commit_transaction+0x94a/0x2480 fs/btrfs/transaction.c:2218
       btrfs_clear_free_space_tree+0x69d/0xa50 fs/btrfs/free-space-tree.c:1255
chnl_net:chnl_net_open(): err: Unable to register and open device, Err:-19
       open_ctree.cold+0x30/0xc3d fs/btrfs/disk-io.c:3203
       btrfs_fill_super fs/btrfs/super.c:1209 [inline]
       btrfs_mount_root+0x12e5/0x1830 fs/btrfs/super.c:1613
       mount_fs+0xa3/0x310 fs/super.c:1261
caif:caif_disconnect_client(): nothing to disconnect
       vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
       vfs_kern_mount+0x3c/0x60 fs/namespace.c:951
       btrfs_mount+0x23a/0xaa0 fs/btrfs/super.c:1681
       mount_fs+0xa3/0x310 fs/super.c:1261
       vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
       vfs_kern_mount fs/namespace.c:951 [inline]
       do_new_mount fs/namespace.c:2492 [inline]
       do_mount+0x115c/0x2f50 fs/namespace.c:2822
       ksys_mount+0xcf/0x130 fs/namespace.c:3038
       __do_sys_mount fs/namespace.c:3052 [inline]
       __se_sys_mount fs/namespace.c:3049 [inline]
       __x64_sys_mount+0xba/0x150 fs/namespace.c:3049
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #5 (&fs_info->tree_log_mutex){+.+.}:
       btrfs_commit_transaction+0x8c2/0x2480 fs/btrfs/transaction.c:2176
       btrfs_clear_free_space_tree+0x69d/0xa50 fs/btrfs/free-space-tree.c:1255
       open_ctree.cold+0x30/0xc3d fs/btrfs/disk-io.c:3203
       btrfs_fill_super fs/btrfs/super.c:1209 [inline]
       btrfs_mount_root+0x12e5/0x1830 fs/btrfs/super.c:1613
       mount_fs+0xa3/0x310 fs/super.c:1261
       vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
       vfs_kern_mount+0x3c/0x60 fs/namespace.c:951
       btrfs_mount+0x23a/0xaa0 fs/btrfs/super.c:1681
       mount_fs+0xa3/0x310 fs/super.c:1261
       vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
       vfs_kern_mount fs/namespace.c:951 [inline]
       do_new_mount fs/namespace.c:2492 [inline]
       do_mount+0x115c/0x2f50 fs/namespace.c:2822
       ksys_mount+0xcf/0x130 fs/namespace.c:3038
       __do_sys_mount fs/namespace.c:3052 [inline]
       __se_sys_mount fs/namespace.c:3049 [inline]
       __x64_sys_mount+0xba/0x150 fs/namespace.c:3049
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #4 (&fs_info->reloc_mutex){+.+.}:
       btrfs_commit_transaction+0x80b/0x2480 fs/btrfs/transaction.c:2120
       btrfs_clear_free_space_tree+0x69d/0xa50 fs/btrfs/free-space-tree.c:1255
       open_ctree.cold+0x30/0xc3d fs/btrfs/disk-io.c:3203
       btrfs_fill_super fs/btrfs/super.c:1209 [inline]
       btrfs_mount_root+0x12e5/0x1830 fs/btrfs/super.c:1613
       mount_fs+0xa3/0x310 fs/super.c:1261
       vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
       vfs_kern_mount+0x3c/0x60 fs/namespace.c:951
       btrfs_mount+0x23a/0xaa0 fs/btrfs/super.c:1681
       mount_fs+0xa3/0x310 fs/super.c:1261
       vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
       vfs_kern_mount fs/namespace.c:951 [inline]
       do_new_mount fs/namespace.c:2492 [inline]
       do_mount+0x115c/0x2f50 fs/namespace.c:2822
       ksys_mount+0xcf/0x130 fs/namespace.c:3038
       __do_sys_mount fs/namespace.c:3052 [inline]
       __se_sys_mount fs/namespace.c:3049 [inline]
       __x64_sys_mount+0xba/0x150 fs/namespace.c:3049
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #3 (sb_internal#2){.+.+}:
       sb_start_intwrite include/linux/fs.h:1626 [inline]
       start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528
       btrfs_dirty_inode+0xe3/0x210 fs/btrfs/inode.c:6165
       btrfs_update_time+0x33b/0x3d0 fs/btrfs/inode.c:6207
       update_time fs/inode.c:1675 [inline]
       touch_atime+0x23c/0x2a0 fs/inode.c:1746
       file_accessed include/linux/fs.h:2123 [inline]
       btrfs_file_mmap+0x11b/0x160 fs/btrfs/file.c:2274
       call_mmap include/linux/fs.h:1826 [inline]
       mmap_region+0xc94/0x16b0 mm/mmap.c:1757
       do_mmap+0x8e8/0x1080 mm/mmap.c:1530
       do_mmap_pgoff include/linux/mm.h:2329 [inline]
       vm_mmap_pgoff+0x197/0x200 mm/util.c:357
       ksys_mmap_pgoff+0x298/0x5a0 mm/mmap.c:1580
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (&mm->mmap_sem){++++}:
       _copy_to_user+0x29/0x100 lib/usercopy.c:25
       copy_to_user include/linux/uaccess.h:155 [inline]
       filldir64+0x26e/0x430 fs/readdir.c:324
       dir_emit_dot include/linux/fs.h:3432 [inline]
       dir_emit_dots include/linux/fs.h:3443 [inline]
       __fat_readdir+0xef1/0x1490 fs/fat/dir.c:575
       iterate_dir+0x473/0x5c0 fs/readdir.c:51
       ksys_getdents64+0x175/0x2b0 fs/readdir.c:357
       __do_sys_getdents64 fs/readdir.c:376 [inline]
       __se_sys_getdents64 fs/readdir.c:373 [inline]
       __x64_sys_getdents64+0x6f/0xb0 fs/readdir.c:373
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&sbi->s_lock){+.+.}:
       fat_write_inode fs/fat/inode.c:911 [inline]
       fat_write_inode+0xfa/0x180 fs/fat/inode.c:904
       write_inode fs/fs-writeback.c:1244 [inline]
       __writeback_single_inode+0x733/0x11d0 fs/fs-writeback.c:1442
       writeback_sb_inodes+0x537/0xef0 fs/fs-writeback.c:1647
       wb_writeback+0x28d/0xcc0 fs/fs-writeback.c:1820
       wb_do_writeback fs/fs-writeback.c:1965 [inline]
       wb_workfn+0x29b/0x1250 fs/fs-writeback.c:2006
       process_one_work+0x864/0x1570 kernel/workqueue.c:2153
       worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
       kthread+0x33f/0x460 kernel/kthread.c:259
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #0 ((work_completion)(&(&wb->dwork)->work)){+.+.}:
       __flush_work+0x542/0x8b0 kernel/workqueue.c:2921
       wb_shutdown+0x172/0x210 mm/backing-dev.c:374
       bdi_unregister+0x169/0x610 mm/backing-dev.c:946
       del_gendisk+0x7f6/0xa80 block/genhd.c:788
       loop_remove drivers/block/loop.c:2066 [inline]
       loop_control_ioctl drivers/block/loop.c:2165 [inline]
       loop_control_ioctl+0x3b1/0x480 drivers/block/loop.c:2131
       vfs_ioctl fs/ioctl.c:46 [inline]
       file_ioctl fs/ioctl.c:501 [inline]
       do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
       ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
       __do_sys_ioctl fs/ioctl.c:712 [inline]
       __se_sys_ioctl fs/ioctl.c:710 [inline]
       __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
  (work_completion)(&(&wb->dwork)->work) --> &bdev->bd_mutex --> loop_ctl_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(loop_ctl_mutex);
                               lock(&bdev->bd_mutex);
                               lock(loop_ctl_mutex);
  lock((work_completion)(&(&wb->dwork)->work));

 *** DEADLOCK ***

1 lock held by syz-executor.1/24902:
 #0: 00000000c499225b (loop_ctl_mutex){+.+.}, at: loop_control_ioctl+0x7b/0x480 drivers/block/loop.c:2137

stack backtrace:
CPU: 0 PID: 24902 Comm: syz-executor.1 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
 check_prev_add kernel/locking/lockdep.c:1866 [inline]
 check_prevs_add kernel/locking/lockdep.c:1979 [inline]
 validate_chain kernel/locking/lockdep.c:2420 [inline]
 __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 __flush_work+0x542/0x8b0 kernel/workqueue.c:2921
 wb_shutdown+0x172/0x210 mm/backing-dev.c:374
 bdi_unregister+0x169/0x610 mm/backing-dev.c:946
 del_gendisk+0x7f6/0xa80 block/genhd.c:788
 loop_remove drivers/block/loop.c:2066 [inline]
 loop_control_ioctl drivers/block/loop.c:2165 [inline]
 loop_control_ioctl+0x3b1/0x480 drivers/block/loop.c:2131
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f86c0b960c9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f86bf108168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f86c0cb5f80 RCX: 00007f86c0b960c9
RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000004
RBP: 00007f86c0bf1ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffef3ec95ff R14: 00007f86bf108300 R15: 0000000000022000
chnl_net:chnl_flowctrl_cb(): NET flowctrl func called flow: CLOSE/DEINIT
chnl_net:chnl_net_open(): state disconnected
A link change request failed with some changes committed already. Interface caif0 may have been left with an inconsistent configuration, please check.
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
overlayfs: fs on './file0' does not support file handles, falling back to index=off,nfs_export=off.
xt_CT: netfilter: NOTRACK target is deprecated, use CT instead or upgrade iptables
kvm [25468]: vcpu0, guest rIP: 0xfff0 Hyper-V unhandled rdmsr: 0x4000001d
overlayfs: fs on './file0' does not support file handles, falling back to index=off,nfs_export=off.
IPVS: ftp: loaded support on port[0] = 21

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/01/06 00:50 linux-4.19.y 3f8a27f9e27b 1dac8c7a .config console log report info [disk image] [vmlinux] ci2-linux-4-19 possible deadlock in loop_control_ioctl
2022/12/20 11:40 linux-4.19.y 3f8a27f9e27b c52b2efb .config console log report info [disk image] [vmlinux] ci2-linux-4-19 possible deadlock in loop_control_ioctl
2022/12/13 16:13 linux-4.19.y 3f8a27f9e27b 67be1ae7 .config console log report info [disk image] [vmlinux] ci2-linux-4-19 possible deadlock in loop_control_ioctl
2022/12/12 16:11 linux-4.19.y 3f8a27f9e27b 67be1ae7 .config console log report info [disk image] [vmlinux] ci2-linux-4-19 possible deadlock in loop_control_ioctl
2022/12/12 14:36 linux-4.19.y 3f8a27f9e27b 67be1ae7 .config console log report info [disk image] [vmlinux] ci2-linux-4-19 possible deadlock in loop_control_ioctl
* Struck through repros no longer work on HEAD.