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Message-ID: <68c6644e.050a0220.50883.0000.GAE@google.com>
Date: Sat, 13 Sep 2025 23:44:30 -0700
From: syzbot <syzbot+e290013facb5d5159eca@...kaller.appspotmail.com>
To: clm@...com, dsterba@...e.com, josef@...icpanda.com,
linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: [syzbot] [btrfs?] possible deadlock in iterate_dir (3)
Hello,
syzbot found the following issue on:
HEAD commit: 9dd1835ecda5 Merge tag 'dma-mapping-6.17-2025-09-09' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16d47562580000
kernel config: https://syzkaller.appspot.com/x/.config?x=429771c55b615e85
dashboard link: https://syzkaller.appspot.com/bug?extid=e290013facb5d5159eca
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63dc392685dc/disk-9dd1835e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3dfcfb97806e/vmlinux-9dd1835e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ddb10128aeb8/bzImage-9dd1835e.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e290013facb5d5159eca@...kaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.243/11919 is trying to acquire lock:
ffff88803c665110 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:462
but task is already holding lock:
ffff8880298fbd68 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (&type->i_mutex_dir_key#5){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_read+0x97/0x1f0 kernel/locking/rwsem.c:1537
inode_lock_shared include/linux/fs.h:885 [inline]
lookup_slow+0x46/0x70 fs/namei.c:1824
walk_component+0x2d2/0x400 fs/namei.c:2129
lookup_last fs/namei.c:2630 [inline]
path_lookupat+0x163/0x430 fs/namei.c:2654
filename_lookup+0x212/0x570 fs/namei.c:2683
kern_path+0x35/0x50 fs/namei.c:2816
is_same_device fs/btrfs/volumes.c:759 [inline]
device_list_add+0xe2a/0x22a0 fs/btrfs/volumes.c:894
btrfs_scan_one_device+0x3ee/0x650 fs/btrfs/volumes.c:1493
btrfs_get_tree_super fs/btrfs/super.c:1853 [inline]
btrfs_get_tree_subvol fs/btrfs/super.c:2077 [inline]
btrfs_get_tree+0x433/0x1820 fs/btrfs/super.c:2111
vfs_get_tree+0x8f/0x2b0 fs/super.c:1815
do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808
do_mount fs/namespace.c:4136 [inline]
__do_sys_mount fs/namespace.c:4347 [inline]
__se_sys_mount+0x317/0x410 fs/namespace.c:4324
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #4 (&fs_devs->device_list_mutex){+.+.}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__mutex_lock_common kernel/locking/rtmutex_api.c:535 [inline]
mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:547
btrfs_run_dev_stats+0x102/0x10e0 fs/btrfs/volumes.c:7772
commit_cowonly_roots+0x1b2/0x860 fs/btrfs/transaction.c:1348
btrfs_commit_transaction+0xfc7/0x3950 fs/btrfs/transaction.c:2462
sync_filesystem+0x1ce/0x250 fs/sync.c:66
__do_sys_syncfs fs/sync.c:160 [inline]
__se_sys_syncfs+0x94/0x110 fs/sync.c:149
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #3 (&fs_info->reloc_mutex){+.+.}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__mutex_lock_common kernel/locking/rtmutex_api.c:535 [inline]
mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:547
btrfs_commit_transaction+0xedd/0x3950 fs/btrfs/transaction.c:2408
sync_filesystem+0x1ce/0x250 fs/sync.c:66
__do_sys_syncfs fs/sync.c:160 [inline]
__se_sys_syncfs+0x94/0x110 fs/sync.c:149
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (btrfs_trans_unblocked){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
wait_current_trans+0x22b/0x520 fs/btrfs/transaction.c:531
start_transaction+0x6d1/0x1620 fs/btrfs/transaction.c:707
btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6235
inode_update_time fs/inode.c:2075 [inline]
touch_atime+0x2f9/0x6d0 fs/inode.c:2148
file_accessed include/linux/fs.h:2664 [inline]
filemap_read+0x100b/0x11a0 mm/filemap.c:2784
__kernel_read+0x4d5/0x970 fs/read_write.c:530
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
ima_calc_file_hash+0x86a/0x1700 security/integrity/ima/ima_crypto.c:568
ima_collect_measurement+0x42e/0x8e0 security/integrity/ima/ima_api.c:293
process_measurement+0x112d/0x1a40 security/integrity/ima/ima_main.c:405
ima_file_check+0xd7/0x120 security/integrity/ima/ima_main.c:633
security_file_post_open+0xbb/0x290 security/security.c:3160
do_open fs/namei.c:3889 [inline]
path_openat+0x2f32/0x3840 fs/namei.c:4046
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1461
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (sb_internal#2){.+.+}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs.h:1799 [inline]
sb_start_intwrite include/linux/fs.h:1982 [inline]
start_transaction+0x56e/0x1620 fs/btrfs/transaction.c:699
btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6235
inode_update_time fs/inode.c:2075 [inline]
touch_atime+0x2f9/0x6d0 fs/inode.c:2148
file_accessed include/linux/fs.h:2664 [inline]
btrfs_file_mmap_prepare+0xde/0x150 fs/btrfs/file.c:2050
vfs_mmap_prepare include/linux/fs.h:2295 [inline]
call_mmap_prepare mm/vma.c:2585 [inline]
__mmap_region mm/vma.c:2653 [inline]
mmap_region+0xb49/0x20a0 mm/vma.c:2739
do_mmap+0xc23/0x10c0 mm/mmap.c:558
vm_mmap_pgoff+0x2a9/0x4d0 mm/util.c:580
ksys_mmap_pgoff+0x4e9/0x720 mm/mmap.c:604
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&mm->mmap_lock){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:462
get_mmap_lock_carefully mm/mmap_lock.c:286 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:337
do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1359
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
user_access_begin arch/x86/include/asm/uaccess.h:-1 [inline]
filldir+0x2a2/0x6c0 fs/readdir.c:290
dir_emit_dot include/linux/fs.h:3963 [inline]
dir_emit_dots include/linux/fs.h:3974 [inline]
offset_readdir+0x1e3/0x560 fs/libfs.c:569
iterate_dir+0x3a2/0x580 fs/readdir.c:108
__do_sys_getdents fs/readdir.c:326 [inline]
__se_sys_getdents+0xe4/0x250 fs/readdir.c:312
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Chain exists of:
&mm->mmap_lock --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#5
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(&type->i_mutex_dir_key#5);
lock(&fs_devs->device_list_mutex);
lock(&type->i_mutex_dir_key#5);
rlock(&mm->mmap_lock);
*** DEADLOCK ***
2 locks held by syz.2.243/11919:
#0: ffff8880302b6928 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x253/0x320 fs/file.c:1232
#1: ffff8880298fbd68 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101
stack backtrace:
CPU: 1 UID: 0 PID: 11919 Comm: syz.2.243 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:462
get_mmap_lock_carefully mm/mmap_lock.c:286 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:337
do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1359
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:filldir+0x2a2/0x6c0 fs/readdir.c:294
Code: 8f ff 4c 89 ff 4c 89 e6 e8 9b 19 8f ff 4d 39 e7 0f 82 7c 02 00 00 49 39 ef 0f 87 73 02 00 00 0f 01 cb 0f ae e8 48 8b 44 24 50 <49> 89 44 24 08 48 8b 4c 24 08 48 8b 44 24 58 48 89 01 48 8b 04 24
RSP: 0018:ffffc9000c6b7c90 EFLAGS: 00050287
RAX: 0000000000000000 RBX: ffffc9000c6b7e38 RCX: ffff88805b34d940
RDX: 0000000000000000 RSI: 0000200000001fc0 RDI: 0000200000001fd8
RBP: 00007ffffffff000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: ffffffff822f4620 R12: 0000200000001fc0
R13: ffffffff8b191ce0 R14: 0000000000000001 R15: 0000200000001fd8
dir_emit_dot include/linux/fs.h:3963 [inline]
dir_emit_dots include/linux/fs.h:3974 [inline]
offset_readdir+0x1e3/0x560 fs/libfs.c:569
iterate_dir+0x3a2/0x580 fs/readdir.c:108
__do_sys_getdents fs/readdir.c:326 [inline]
__se_sys_getdents+0xe4/0x250 fs/readdir.c:312
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f974ee8eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9744ccd038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f974f0d6090 RCX: 00007f974ee8eba9
RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000004
RBP: 00007f974ef11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f974f0d6128 R14: 00007f974f0d6090 R15: 00007ffce04f3a78
</TASK>
----------------
Code disassembly (best guess), 1 bytes skipped:
0: ff 4c 89 ff decl -0x1(%rcx,%rcx,4)
4: 4c 89 e6 mov %r12,%rsi
7: e8 9b 19 8f ff call 0xff8f19a7
c: 4d 39 e7 cmp %r12,%r15
f: 0f 82 7c 02 00 00 jb 0x291
15: 49 39 ef cmp %rbp,%r15
18: 0f 87 73 02 00 00 ja 0x291
1e: 0f 01 cb stac
21: 0f ae e8 lfence
24: 48 8b 44 24 50 mov 0x50(%rsp),%rax
* 29: 49 89 44 24 08 mov %rax,0x8(%r12) <-- trapping instruction
2e: 48 8b 4c 24 08 mov 0x8(%rsp),%rcx
33: 48 8b 44 24 58 mov 0x58(%rsp),%rax
38: 48 89 01 mov %rax,(%rcx)
3b: 48 8b 04 24 mov (%rsp),%rax
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
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