* [syzbot] [fs?] possible deadlock in configfs_detach_group
@ 2026-08-11 0:24 syzbot
0 siblings, 0 replies; only message in thread
From: syzbot @ 2026-08-11 0:24 UTC (permalink / raw)
To: a.hindborg, leitao, linux-fsdevel, linux-kernel, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: c21bb4193868 Merge tag 'for_linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14a63bb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f221a1b5d497ed15
dashboard link: https://syzkaller.appspot.com/bug?extid=245b08b227dcdeb63e2c
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c21bb419.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ff1def389cf6/vmlinux-c21bb419.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ab751d30f9d2/bzImage-c21bb419.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+245b08b227dcdeb63e2c@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.304/7178 is trying to acquire lock:
ffff8880005e4880 (&default_group_class[depth - 1]#9){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
ffff8880005e4880 (&default_group_class[depth - 1]#9){+.+.}-{4:4}, at: detach_groups fs/configfs/dir.c:680 [inline]
ffff8880005e4880 (&default_group_class[depth - 1]#9){+.+.}-{4:4}, at: configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
but task is already holding lock:
ffff8880005e1900 (&default_group_class[depth - 1]#8){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
ffff8880005e1900 (&default_group_class[depth - 1]#8){++++}-{4:4}, at: detach_groups fs/configfs/dir.c:680 [inline]
ffff8880005e1900 (&default_group_class[depth - 1]#8){++++}-{4:4}, at: configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (&default_group_class[depth - 1]#8){++++}-{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]
detach_groups fs/configfs/dir.c:680 [inline]
configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
detach_groups fs/configfs/dir.c:682 [inline]
configfs_detach_group+0x224/0x440 fs/configfs/dir.c:887
configfs_rmdir+0x598/0x950 fs/configfs/dir.c:1554
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_rmdir fs/namei.c:5461 [inline]
__se_sys_rmdir fs/namei.c:5458 [inline]
__ia32_sys_rmdir+0x45/0x60 fs/namei.c:5458
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
-> #4 (&default_group_class[depth - 1]#2){+.+.}-{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]
detach_groups fs/configfs/dir.c:680 [inline]
configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
configfs_rmdir+0x598/0x950 fs/configfs/dir.c:1554
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_rmdir fs/namei.c:5461 [inline]
__se_sys_rmdir fs/namei.c:5458 [inline]
__ia32_sys_rmdir+0x45/0x60 fs/namei.c:5458
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
-> #3 (&sb->s_type->i_mutex_key#26){++++}-{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]
__ia32_sys_mkdir+0x6a/0x90 fs/namei.c:5333
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
-> #2 (&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]
__ia32_sys_mkdir+0x6a/0x90 fs/namei.c:5333
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
-> #1 (gadget_subsys.su_mutex){+.+.}-{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
uvcg_streaming_class_allow_link+0x100/0x6b0 drivers/usb/gadget/function/uvc_configfs.c:3432
configfs_symlink+0x540/0x11f0 fs/configfs/symlink.c:196
vfs_symlink fs/namei.c:5660 [inline]
vfs_symlink+0x178/0x4d0 fs/namei.c:5639
filename_symlinkat+0x2a6/0x560 fs/namei.c:5685
__do_sys_symlinkat fs/namei.c:5705 [inline]
__se_sys_symlinkat fs/namei.c:5700 [inline]
__ia32_sys_symlinkat+0x9b/0xe0 fs/namei.c:5700
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
-> #0 (&default_group_class[depth - 1]#9){+.+.}-{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
down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631
inode_lock include/linux/fs.h:1024 [inline]
detach_groups fs/configfs/dir.c:680 [inline]
configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
detach_groups fs/configfs/dir.c:682 [inline]
configfs_detach_group+0x224/0x440 fs/configfs/dir.c:887
detach_groups fs/configfs/dir.c:682 [inline]
configfs_detach_group+0x224/0x440 fs/configfs/dir.c:887
configfs_rmdir+0x598/0x950 fs/configfs/dir.c:1554
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_rmdir fs/namei.c:5461 [inline]
__se_sys_rmdir fs/namei.c:5458 [inline]
__ia32_sys_rmdir+0x45/0x60 fs/namei.c:5458
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
other info that might help us debug this:
Chain exists of:
&default_group_class[depth - 1]#9 --> &default_group_class[depth - 1]#2 --> &default_group_class[depth - 1]#8
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&default_group_class[depth - 1]#8);
lock(&default_group_class[depth - 1]#2);
lock(&default_group_class[depth - 1]#8);
lock(&default_group_class[depth - 1]#9);
*** DEADLOCK ***
5 locks held by syz.3.304/7178:
#0: ffff88802250c450 (sb_writers#15){.+.+}-{0:0}, at: filename_rmdir+0x1ff/0x5c0 fs/namei.c:5427
#1: ffff888013f76e80 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#1: ffff888013f76e80 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
#1: ffff888013f76e80 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
#1: ffff888013f76e80 (&default_group_class[depth - 1]#2/1){+.+.}-{4:4}, at: filename_rmdir+0x258/0x5c0 fs/namei.c:5431
#2: ffff8880005e0f80 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
#2: ffff8880005e0f80 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: vfs_rmdir fs/namei.c:5366 [inline]
#2: ffff8880005e0f80 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: vfs_rmdir+0xed/0x8a0 fs/namei.c:5354
#3: ffff8880005e6e80 (&default_group_class[depth - 1]#2){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
#3: ffff8880005e6e80 (&default_group_class[depth - 1]#2){+.+.}-{4:4}, at: detach_groups fs/configfs/dir.c:680 [inline]
#3: ffff8880005e6e80 (&default_group_class[depth - 1]#2){+.+.}-{4:4}, at: configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
#4: ffff8880005e1900 (&default_group_class[depth - 1]#8){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
#4: ffff8880005e1900 (&default_group_class[depth - 1]#8){++++}-{4:4}, at: detach_groups fs/configfs/dir.c:680 [inline]
#4: ffff8880005e1900 (&default_group_class[depth - 1]#8){++++}-{4:4}, at: configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
stack backtrace:
CPU: 3 UID: 0 PID: 7178 Comm: syz.3.304 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
down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631
inode_lock include/linux/fs.h:1024 [inline]
detach_groups fs/configfs/dir.c:680 [inline]
configfs_detach_group+0x21c/0x440 fs/configfs/dir.c:887
detach_groups fs/configfs/dir.c:682 [inline]
configfs_detach_group+0x224/0x440 fs/configfs/dir.c:887
detach_groups fs/configfs/dir.c:682 [inline]
configfs_detach_group+0x224/0x440 fs/configfs/dir.c:887
configfs_rmdir+0x598/0x950 fs/configfs/dir.c:1554
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_rmdir fs/namei.c:5461 [inline]
__se_sys_rmdir fs/namei.c:5458 [inline]
__ia32_sys_rmdir+0x45/0x60 fs/namei.c:5458
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7ff3fec
Code: Unable to access opcode bytes at 0xf7ff3fc2.
RSP: 002b:00000000f54b650c EFLAGS: 00000292 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000080000200 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
---
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2026-08-11 0:24 [syzbot] [fs?] possible deadlock in configfs_detach_group syzbot
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