possible deadlock in lookup_slow

Status: auto-obsoleted due to no activity on 2023/12/11 13:10
Reported-by: syzbot+3d98c42ea36505a1a0a6@syzkaller.appspotmail.com
First crash: 1260d, last: 1088d
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in lookup_slow (3) prio:low kernfs 4 syz, C 517 1d21h 1133d 0/29 upstream: reported C repro on 2023/07/19 13:17
linux-4.19 possible deadlock in lookup_slow 4 22 2263d 2689d 0/1 auto-closed as invalid on 2020/10/12 22:59
linux-6.1 possible deadlock in lookup_slow 4 1 571d 571d 0/3 auto-obsoleted due to no activity on 2025/05/11 18:32
upstream possible deadlock in lookup_slow fs 4 139 2649d 2890d 0/29 auto-closed as invalid on 2019/10/25 08:42
linux-6.1 possible deadlock in lookup_slow (2) 4 15 4d01h 466d 0/3 upstream: reported on 2025/05/16 17:47
linux-5.15 possible deadlock in lookup_slow (2) origin:lts-only 4 syz, C inconclusive 137 3d05h 986d 0/3 upstream: reported C repro on 2023/12/13 22:35
linux-4.14 possible deadlock in lookup_slow 4 syz, C 2027 1268d 2559d 0/1 upstream: reported C repro on 2019/08/24 01:53
upstream possible deadlock in lookup_slow (2) fs 4 7 2417d 2462d 0/29 auto-closed as invalid on 2020/05/11 09:17

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
5.15.130-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/7597 is trying to acquire lock:
ffff0000d8a23fc0 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:797 [inline]
ffff0000d8a23fc0 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: lookup_slow+0x50/0x84 fs/namei.c:1675

but task is already holding lock:
ffff0000d42850e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_free_stale_devices+0x158/0x9ec fs/btrfs/volumes.c:603

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
       insert_dev_extents fs/btrfs/block-group.c:2379 [inline]
       btrfs_create_pending_block_groups+0x490/0xebc fs/btrfs/block-group.c:2429
       __btrfs_end_transaction+0x13c/0x610 fs/btrfs/transaction.c:1013
       btrfs_end_transaction+0x24/0x34 fs/btrfs/transaction.c:1049
       flush_space+0x458/0xc94 fs/btrfs/space-info.c:674
       btrfs_async_reclaim_data_space+0xec/0x37c fs/btrfs/space-info.c:1169
       process_one_work+0x790/0x11b8 kernel/workqueue.c:2310
       worker_thread+0x910/0x1034 kernel/workqueue.c:2457
       kthread+0x37c/0x45c kernel/kthread.c:319
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870

-> #3 (sb_internal#3){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1742 [inline]
       sb_start_intwrite include/linux/fs.h:1859 [inline]
       start_transaction+0x644/0x1480 fs/btrfs/transaction.c:677
       btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:790
       btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6322
       btrfs_update_time+0x248/0x270 fs/btrfs/inode.c:6364
       inode_update_time fs/inode.c:1829 [inline]
       file_update_time+0x35c/0x3f0 fs/inode.c:2019
       btrfs_page_mkwrite+0x464/0xde8 fs/btrfs/inode.c:8875
       do_page_mkwrite+0x144/0x37c mm/memory.c:2892
       do_shared_fault mm/memory.c:4298 [inline]
       do_fault mm/memory.c:4366 [inline]
       handle_pte_fault mm/memory.c:4621 [inline]
       __handle_mm_fault mm/memory.c:4756 [inline]
       handle_mm_fault+0x1b0c/0x33c4 mm/memory.c:4854
       __do_page_fault arch/arm64/mm/fault.c:505 [inline]
       do_page_fault+0x700/0xb60 arch/arm64/mm/fault.c:605
       do_translation_fault+0xe8/0x138 arch/arm64/mm/fault.c:686
       do_mem_abort+0x70/0x1d8 arch/arm64/mm/fault.c:819
       el0_da+0x94/0x20c arch/arm64/kernel/entry-common.c:482
       el0t_64_sync_handler+0xc0/0xe4 arch/arm64/kernel/entry-common.c:617
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #2 (sb_pagefaults#3){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1742 [inline]
       sb_start_pagefault include/linux/fs.h:1841 [inline]
       btrfs_page_mkwrite+0x254/0xde8 fs/btrfs/inode.c:8859
       do_page_mkwrite+0x144/0x37c mm/memory.c:2892
       do_shared_fault mm/memory.c:4298 [inline]
       do_fault mm/memory.c:4366 [inline]
       handle_pte_fault mm/memory.c:4621 [inline]
       __handle_mm_fault mm/memory.c:4756 [inline]
       handle_mm_fault+0x1b0c/0x33c4 mm/memory.c:4854
       __do_page_fault arch/arm64/mm/fault.c:505 [inline]
       do_page_fault+0x700/0xb60 arch/arm64/mm/fault.c:605
       do_translation_fault+0xe8/0x138 arch/arm64/mm/fault.c:686
       do_mem_abort+0x70/0x1d8 arch/arm64/mm/fault.c:819
       el0_da+0x94/0x20c arch/arm64/kernel/entry-common.c:482
       el0t_64_sync_handler+0xc0/0xe4 arch/arm64/kernel/entry-common.c:617
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&mm->mmap_lock){++++}-{3:3}:
       __might_fault+0xc8/0x128 mm/memory.c:5324
       filldir64+0x2bc/0x9e4 fs/readdir.c:335
       dir_emit include/linux/fs.h:3603 [inline]
       call_filldir fs/ext4/dir.c:537 [inline]
       ext4_dx_readdir fs/ext4/dir.c:613 [inline]
       ext4_readdir+0x2a18/0x3224 fs/ext4/dir.c:142
       iterate_dir+0x1f4/0x4e4
       __do_sys_getdents64 fs/readdir.c:369 [inline]
       __se_sys_getdents64 fs/readdir.c:354 [inline]
       __arm64_sys_getdents64+0x1c4/0x4c4 fs/readdir.c:354
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596
       el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (&type->i_mutex_dir_key#3){++++}-{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:3787 [inline]
       __lock_acquire+0x32cc/0x7620 kernel/locking/lockdep.c:5011
       lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5622
       down_read+0xc0/0x398 kernel/locking/rwsem.c:1488
       inode_lock_shared include/linux/fs.h:797 [inline]
       lookup_slow+0x50/0x84 fs/namei.c:1675
       walk_component+0x394/0x4cc fs/namei.c:1972
       lookup_last fs/namei.c:2427 [inline]
       path_lookupat+0x13c/0x3d0 fs/namei.c:2451
       filename_lookup+0x1c4/0x4c8 fs/namei.c:2480
       kern_path+0x4c/0x194 fs/namei.c:2570
       lookup_bdev+0xc0/0x25c block/bdev.c:979
       device_matched fs/btrfs/volumes.c:568 [inline]
       btrfs_free_stale_devices+0x658/0x9ec fs/btrfs/volumes.c:608
       btrfs_forget_devices+0x5c/0x98 fs/btrfs/volumes.c:1380
       btrfs_control_ioctl+0x12c/0x248 fs/btrfs/super.c:2451
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl fs/ioctl.c:860 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596
       el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
  &type->i_mutex_dir_key#3 --> sb_internal#3 --> &fs_devs->device_list_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&fs_devs->device_list_mutex);
                               lock(sb_internal#3);
                               lock(&fs_devs->device_list_mutex);
  lock(&type->i_mutex_dir_key#3);

 *** DEADLOCK ***

2 locks held by syz-executor.2/7597:
 #0: ffff800014f95988 (uuid_mutex){+.+.}-{3:3}, at: btrfs_forget_devices+0x28/0x98 fs/btrfs/volumes.c:1379
 #1: ffff0000d42850e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_free_stale_devices+0x158/0x9ec fs/btrfs/volumes.c:603

stack backtrace:
CPU: 0 PID: 7597 Comm: syz-executor.2 Not tainted 5.15.130-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call trace:
 dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2011
 check_noncircular+0x2cc/0x378 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:3787 [inline]
 __lock_acquire+0x32cc/0x7620 kernel/locking/lockdep.c:5011
 lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5622
 down_read+0xc0/0x398 kernel/locking/rwsem.c:1488
 inode_lock_shared include/linux/fs.h:797 [inline]
 lookup_slow+0x50/0x84 fs/namei.c:1675
 walk_component+0x394/0x4cc fs/namei.c:1972
 lookup_last fs/namei.c:2427 [inline]
 path_lookupat+0x13c/0x3d0 fs/namei.c:2451
 filename_lookup+0x1c4/0x4c8 fs/namei.c:2480
 kern_path+0x4c/0x194 fs/namei.c:2570
 lookup_bdev+0xc0/0x25c block/bdev.c:979
 device_matched fs/btrfs/volumes.c:568 [inline]
 btrfs_free_stale_devices+0x658/0x9ec fs/btrfs/volumes.c:608
 btrfs_forget_devices+0x5c/0x98 fs/btrfs/volumes.c:1380
 btrfs_control_ioctl+0x12c/0x248 fs/btrfs/super.c:2451
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:596
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:614
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/09/02 13:09 linux-5.15.y 8f790700c974 696ea0d2 .config console log report info ci2-linux-5-15-kasan-arm64 possible deadlock in lookup_slow
2023/07/26 13:27 linux-5.15.y 5c6a716301d9 2a509c27 .config console log report info ci2-linux-5-15-kasan possible deadlock in lookup_slow
2023/07/15 00:40 linux-5.15.y d54cfc420586 35d9ecc5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in lookup_slow
2023/07/13 20:12 linux-5.15.y d54cfc420586 55eda22f .config console log report info ci2-linux-5-15-kasan possible deadlock in lookup_slow
2023/05/01 04:32 linux-5.15.y 8a7f2a5c5aa1 62df2017 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in lookup_slow
2023/04/25 06:42 linux-5.15.y 3299fb36854f 65320f8e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in lookup_slow
2023/03/14 15:40 linux-5.15.y 2ddbd0f967b3 0d5c4377 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in lookup_slow
2023/07/27 13:50 linux-5.15.y 09996673e313 92476829 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in lookup_slow
2023/06/13 20:53 linux-5.15.y 7349e40704a0 d2ee9228 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in lookup_slow
2023/05/28 07:45 linux-5.15.y 1fe619a7d252 cf184559 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in lookup_slow
2023/05/25 13:16 linux-5.15.y 1fe619a7d252 0513b3e6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in lookup_slow
* Struck through repros no longer work on HEAD.