Re: [syzbot] [fs?] possible deadlock in configfs_rmdir
From: syzbot
Date: Wed Jul 29 2026 - 06:44:50 EST
syzbot has found a reproducer for the following issue on:
HEAD commit: fc02acf6ac0c Merge tag 'platform-drivers-x86-v7.2-4' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15db5632580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=c9f9d646b08f3b6032fe
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1496003e580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=142017b1580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-fc02acf6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/eca05900a79c/vmlinux-fc02acf6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e655b72e0b5f/bzImage-fc02acf6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c9f9d646b08f3b6032fe@xxxxxxxxxxxxxxxxxxxxxxxxx
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.18/5928 is trying to acquire lock:
ffffffff901d0908 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: configfs_rmdir+0x5ae/0x950 fs/configfs/dir.c:1556
but task is already holding lock:
ffff88803aa6f800 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
ffff88803aa6f800 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: vfs_rmdir fs/namei.c:5366 [inline]
ffff88803aa6f800 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: vfs_rmdir+0xed/0x8a0 fs/namei.c:5354
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}:
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631
inode_lock include/linux/fs.h:1024 [inline]
configfs_depend_item_unlocked+0xf3/0x6a0 fs/configfs/dir.c:1259
usbg_make_tpg+0x261/0x620 drivers/usb/gadget/function/f_tcm.c:1686
target_fabric_make_tpg+0xab/0x8c0 drivers/target/target_core_fabric_configfs.c:939
configfs_mkdir+0x51e/0xb70 fs/configfs/dir.c:1360
vfs_mkdir+0x361/0x850 fs/namei.c:5276
filename_mkdirat+0x48b/0x5e0 fs/namei.c:5309
__do_sys_mkdir fs/namei.c:5336 [inline]
__se_sys_mkdir fs/namei.c:5333 [inline]
__x64_sys_mkdir+0x6b/0x90 fs/namei.c:5333
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&opts->dep_lock){+.+.}-{4:4}:
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
tcm_set_name+0x29/0xb0 drivers/usb/gadget/function/f_tcm.c:2669
function_make+0x21c/0x3f0 drivers/usb/gadget/configfs.c:636
configfs_mkdir+0x51e/0xb70 fs/configfs/dir.c:1360
vfs_mkdir+0x361/0x850 fs/namei.c:5276
filename_mkdirat+0x48b/0x5e0 fs/namei.c:5309
__do_sys_mkdir fs/namei.c:5336 [inline]
__se_sys_mkdir fs/namei.c:5333 [inline]
__x64_sys_mkdir+0x6b/0x90 fs/namei.c:5333
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}:
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
configfs_rmdir+0x5ae/0x950 fs/configfs/dir.c:1556
vfs_rmdir fs/namei.c:5381 [inline]
vfs_rmdir+0x328/0x8a0 fs/namei.c:5354
filename_rmdir+0x31a/0x5c0 fs/namei.c:5438
__do_sys_unlinkat fs/namei.c:5613 [inline]
__se_sys_unlinkat fs/namei.c:5606 [inline]
__x64_sys_unlinkat+0xf5/0x130 fs/namei.c:5606
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 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:
gadget_subsys.su_mutex --> &opts->dep_lock --> &sb->s_type->i_mutex_key#24
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#24);
lock(&opts->dep_lock);
lock(&sb->s_type->i_mutex_key#24);
lock(gadget_subsys.su_mutex);
*** DEADLOCK ***
3 locks held by syz.0.18/5928:
#0: ffff888023d44450 (sb_writers#13){.+.+}-{0:0}, at: filename_rmdir+0x1ff/0x5c0 fs/namei.c:5427
#1: ffff888047c6e9c0 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#1: ffff888047c6e9c0 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
#1: ffff888047c6e9c0 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
#1: ffff888047c6e9c0 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: filename_rmdir+0x258/0x5c0 fs/namei.c:5431
#2: ffff88803aa6f800 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
#2: ffff88803aa6f800 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: vfs_rmdir fs/namei.c:5366 [inline]
#2: ffff88803aa6f800 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: vfs_rmdir+0xed/0x8a0 fs/namei.c:5354
stack backtrace:
CPU: 3 UID: 0 PID: 5928 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
configfs_rmdir+0x5ae/0x950 fs/configfs/dir.c:1556
vfs_rmdir fs/namei.c:5381 [inline]
vfs_rmdir+0x328/0x8a0 fs/namei.c:5354
filename_rmdir+0x31a/0x5c0 fs/namei.c:5438
__do_sys_unlinkat fs/namei.c:5613 [inline]
__se_sys_unlinkat fs/namei.c:5606 [inline]
__x64_sys_unlinkat+0xf5/0x130 fs/namei.c:5606
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f838c39de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd033e6618 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f838c625fa0 RCX: 00007f838c39de99
RDX: 0000000000000200 RSI: 0000200000000480 RDI: ffffffffffffff9c
RBP: 00007f838c433eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f838c625fac R14: 00007f838c625fa0 R15: 00007f838c625fa0
</TASK>
---
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#syz test: git://repo/address.git branch-or-commit-hash
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