[v5.15] possible deadlock in configfs_rmdir

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syzbot

unread,
Jul 24, 2026, 6:09:27 PM (2 days ago) Jul 24
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12502449580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=132c7bcda75d8f9df336
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+132c7b...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.6.2210/11902 is trying to acquire lock:
ffffffff8ceceff0 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556

but task is already holding lock:
ffff88807783a9d0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
ffff88807783a9d0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: vfs_rmdir+0xe1/0x410 fs/namei.c:4147

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#21){++++}-{3:3}:
down_write+0x38/0x60 kernel/locking/rwsem.c:1551
inode_lock include/linux/fs.h:787 [inline]
configfs_depend_item_unlocked+0x14f/0x430 fs/configfs/dir.c:1255
usbg_make_tpg+0x1f3/0x580 drivers/usb/gadget/function/f_tcm.c:1351
target_fabric_make_tpg+0xa0/0x6d0 drivers/target/target_core_fabric_configfs.c:837
configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x386/0x570 fs/namei.c:4073
do_mkdirat+0x1dd/0x5c0 fs/namei.c:4098
__do_sys_mkdirat fs/namei.c:4113 [inline]
__se_sys_mkdirat fs/namei.c:4111 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4111
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&opts->dep_lock){+.+.}-{3:3}:
__mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
tcm_set_name+0x26/0x90 drivers/usb/gadget/function/f_tcm.c:2224
function_make+0x195/0x350 drivers/usb/gadget/configfs.c:620
configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x386/0x570 fs/namei.c:4073
do_mkdirat+0x1dd/0x5c0 fs/namei.c:4098
__do_sys_mkdirat fs/namei.c:4113 [inline]
__se_sys_mkdirat fs/namei.c:4111 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4111
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (gadget_subsys.su_mutex){+.+.}-{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:3788 [inline]
__lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x19d/0x410 fs/namei.c:4157
do_rmdir+0x27f/0x710 fs/namei.c:4218
__do_sys_rmdir fs/namei.c:4237 [inline]
__se_sys_rmdir fs/namei.c:4235 [inline]
__x64_sys_rmdir+0x45/0x50 fs/namei.c:4235
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
gadget_subsys.su_mutex --> &opts->dep_lock --> &sb->s_type->i_mutex_key#21

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#21);
lock(&opts->dep_lock);
lock(&sb->s_type->i_mutex_key#21);
lock(gadget_subsys.su_mutex);

*** DEADLOCK ***

3 locks held by syz.6.2210/11902:
#0: ffff88801de08460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:386
#1: ffff88805ff2d080 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
#1: ffff88805ff2d080 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: do_rmdir+0x1b0/0x710 fs/namei.c:4205
#2: ffff88807783a9d0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
#2: ffff88807783a9d0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: vfs_rmdir+0xe1/0x410 fs/namei.c:4147

stack backtrace:
CPU: 1 PID: 11902 Comm: syz.6.2210 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
check_noncircular+0x296/0x330 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:3788 [inline]
__lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x19d/0x410 fs/namei.c:4157
do_rmdir+0x27f/0x710 fs/namei.c:4218
__do_sys_rmdir fs/namei.c:4237 [inline]
__se_sys_rmdir fs/namei.c:4235 [inline]
__x64_sys_rmdir+0x45/0x50 fs/namei.c:4235
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd386acee99
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:00007fd384d27028 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 00007fd386d56fa0 RCX: 00007fd386acee99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000800
RBP: 00007fd386b64eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd386d57038 R14: 00007fd386d56fa0 R15: 00007ffea0332aa8
</TASK>


---
This report is generated by a bot. It may contain errors.
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syzbot

unread,
Jul 25, 2026, 5:00:28 AM (20 hours ago) Jul 25
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=172a2232580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=f361b5d29e9e40b9fe3f
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a9aa438e39c2/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a7b5afd2e170/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c7673d370fb/bzImage-dc5c83b7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f361b5...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.326/5595 is trying to acquire lock:
ffffffff8d7b2f90 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556

but task is already holding lock:
ffff8880556b9fb0 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
ffff8880556b9fb0 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: vfs_rmdir+0xea/0x4a0 fs/namei.c:4188

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#24){++++}-{3:3}:
down_write+0x36/0x60 kernel/locking/rwsem.c:1573
inode_lock include/linux/fs.h:758 [inline]
configfs_depend_item_unlocked+0x14f/0x430 fs/configfs/dir.c:1255
usbg_make_tpg+0x1f3/0x580 drivers/usb/gadget/function/f_tcm.c:1365
target_fabric_make_tpg+0xa0/0x6d0 drivers/target/target_core_fabric_configfs.c:905
configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x386/0x570 fs/namei.c:4114
do_mkdirat+0x1d8/0x440 fs/namei.c:4139
__do_sys_mkdir fs/namei.c:4159 [inline]
__se_sys_mkdir fs/namei.c:4157 [inline]
__x64_sys_mkdir+0x6a/0x80 fs/namei.c:4157
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&opts->dep_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
tcm_set_name+0x26/0x90 drivers/usb/gadget/function/f_tcm.c:2219
function_make+0x195/0x350 drivers/usb/gadget/configfs.c:625
configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x386/0x570 fs/namei.c:4114
do_mkdirat+0x1d8/0x440 fs/namei.c:4139
__do_sys_mkdir fs/namei.c:4159 [inline]
__se_sys_mkdir fs/namei.c:4157 [inline]
__x64_sys_mkdir+0x6a/0x80 fs/namei.c:4157
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (gadget_subsys.su_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3830 [inline]
__lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x34e/0x4a0 fs/namei.c:4199
do_rmdir+0x29a/0x5c0 fs/namei.c:4260
__do_sys_rmdir fs/namei.c:4279 [inline]
__se_sys_rmdir fs/namei.c:4277 [inline]
__x64_sys_rmdir+0x45/0x50 fs/namei.c:4277
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

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.1.326/5595:
#0: ffff888146e80460 (sb_writers#17){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:402
#1: ffff8880554d1aa0 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:793 [inline]
#1: ffff8880554d1aa0 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: do_rmdir+0x1b7/0x5c0 fs/namei.c:4247
#2: ffff8880556b9fb0 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
#2: ffff8880556b9fb0 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: vfs_rmdir+0xea/0x4a0 fs/namei.c:4188

stack backtrace:
CPU: 1 PID: 5595 Comm: syz.1.326 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3830 [inline]
__lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x34e/0x4a0 fs/namei.c:4199
do_rmdir+0x29a/0x5c0 fs/namei.c:4260
__do_sys_rmdir fs/namei.c:4279 [inline]
__se_sys_rmdir fs/namei.c:4277 [inline]
__x64_sys_rmdir+0x45/0x50 fs/namei.c:4277
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f05e6d9de99
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:00007f05e7c7a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 00007f05e7026090 RCX: 00007f05e6d9de99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000000
RBP: 00007f05e6e33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f05e7026128 R14: 00007f05e7026090 R15: 00007ffcca2f8a78

syzbot

unread,
Jul 25, 2026, 12:49:29 PM (12 hours ago) Jul 25
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: c5596480c50e Linux 6.6.145
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=159d3746580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=22a2e230e9367df26d4a
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/eb5cda0a8020/disk-c5596480.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca05ff2fc502/vmlinux-c5596480.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6daf3255b985/bzImage-c5596480.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+22a2e2...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.984/10648 is trying to acquire lock:
ffffffff8ddf6d10 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: configfs_rmdir+0x63c/0x980 fs/configfs/dir.c:1556

but task is already holding lock:
ffff88807a367400 (&sb->s_type->i_mutex_key#28){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
ffff88807a367400 (&sb->s_type->i_mutex_key#28){++++}-{3:3}, at: vfs_rmdir+0xee/0x4b0 fs/namei.c:4197

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#28){++++}-{3:3}:
down_write+0x97/0x200 kernel/locking/rwsem.c:1573
inode_lock include/linux/fs.h:804 [inline]
configfs_depend_item_unlocked+0x157/0x430 fs/configfs/dir.c:1255
usbg_make_tpg+0x1f7/0x580 drivers/usb/gadget/function/f_tcm.c:1341
target_fabric_make_tpg+0xa4/0x6d0 drivers/target/target_core_fabric_configfs.c:939
configfs_mkdir+0x515/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x2a5/0x470 fs/namei.c:4125
do_mkdirat+0x1dc/0x450 fs/namei.c:4148
__do_sys_mkdirat fs/namei.c:4163 [inline]
__se_sys_mkdirat fs/namei.c:4161 [inline]
__x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4161
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&opts->dep_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
tcm_set_name+0x2a/0x90 drivers/usb/gadget/function/f_tcm.c:2188
function_make+0x199/0x350 drivers/usb/gadget/configfs.c:635
configfs_mkdir+0x515/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x2a5/0x470 fs/namei.c:4125
do_mkdirat+0x1dc/0x450 fs/namei.c:4148
__do_sys_mkdirat fs/namei.c:4163 [inline]
__se_sys_mkdirat fs/namei.c:4161 [inline]
__x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4161
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (gadget_subsys.su_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
configfs_rmdir+0x63c/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x352/0x4b0 fs/namei.c:4208
do_rmdir+0x29f/0x590 fs/namei.c:4267
__do_sys_unlinkat fs/namei.c:4445 [inline]
__se_sys_unlinkat fs/namei.c:4439 [inline]
__x64_sys_unlinkat+0xc4/0xe0 fs/namei.c:4439
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
gadget_subsys.su_mutex --> &opts->dep_lock --> &sb->s_type->i_mutex_key#28

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#28);
lock(&opts->dep_lock);
lock(&sb->s_type->i_mutex_key#28);
lock(gadget_subsys.su_mutex);

*** DEADLOCK ***

3 locks held by syz.4.984/10648:
#0: ffff88801877c418 (sb_writers#23){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:412
#1: ffff88807a20d090 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:839 [inline]
#1: ffff88807a20d090 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: do_rmdir+0x1c6/0x590 fs/namei.c:4255
#2: ffff88807a367400 (&sb->s_type->i_mutex_key#28){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
#2: ffff88807a367400 (&sb->s_type->i_mutex_key#28){++++}-{3:3}, at: vfs_rmdir+0xee/0x4b0 fs/namei.c:4197

stack backtrace:
CPU: 1 PID: 10648 Comm: syz.4.984 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
configfs_rmdir+0x63c/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x352/0x4b0 fs/namei.c:4208
do_rmdir+0x29f/0x590 fs/namei.c:4267
__do_sys_unlinkat fs/namei.c:4445 [inline]
__se_sys_unlinkat fs/namei.c:4439 [inline]
__x64_sys_unlinkat+0xc4/0xe0 fs/namei.c:4439
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f58c319de99
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:00007f58c40ba028 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f58c3425fa0 RCX: 00007f58c319de99
RDX: 0000000000000200 RSI: 0000200000000480 RDI: ffffffffffffff9c
RBP: 00007f58c3233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f58c3426038 R14: 00007f58c3425fa0 R15: 00007ffefb23faf8

syzbot

unread,
Jul 25, 2026, 10:26:31 PM (3 hours ago) Jul 25
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13c246b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=132c7bcda75d8f9df336
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=125a66b9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147fd88e580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+132c7b...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.18/4318 is trying to acquire lock:
ffffffff8ceceff0 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556

but task is already holding lock:
ffff88805ce1f3f0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
ffff88805ce1f3f0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: vfs_rmdir+0xe1/0x410 fs/namei.c:4147

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}:
down_write+0x38/0x60 kernel/locking/rwsem.c:1551
inode_lock include/linux/fs.h:787 [inline]
configfs_depend_item_unlocked+0x14f/0x430 fs/configfs/dir.c:1255
usbg_make_tpg+0x1f3/0x580 drivers/usb/gadget/function/f_tcm.c:1351
target_fabric_make_tpg+0xa0/0x6d0 drivers/target/target_core_fabric_configfs.c:837
configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x386/0x570 fs/namei.c:4073
do_mkdirat+0x1dd/0x5c0 fs/namei.c:4098
__do_sys_mkdir fs/namei.c:4118 [inline]
__se_sys_mkdir fs/namei.c:4116 [inline]
__x64_sys_mkdir+0x6a/0x80 fs/namei.c:4116
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&opts->dep_lock){+.+.}-{3:3}:
__mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
tcm_set_name+0x26/0x90 drivers/usb/gadget/function/f_tcm.c:2224
function_make+0x195/0x350 drivers/usb/gadget/configfs.c:620
configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x386/0x570 fs/namei.c:4073
do_mkdirat+0x1dd/0x5c0 fs/namei.c:4098
__do_sys_mkdir fs/namei.c:4118 [inline]
__se_sys_mkdir fs/namei.c:4116 [inline]
__x64_sys_mkdir+0x6a/0x80 fs/namei.c:4116
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (gadget_subsys.su_mutex){+.+.}-{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:3788 [inline]
__lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x19d/0x410 fs/namei.c:4157
do_rmdir+0x27f/0x710 fs/namei.c:4218
__do_sys_unlinkat fs/namei.c:4398 [inline]
__se_sys_unlinkat fs/namei.c:4392 [inline]
__x64_sys_unlinkat+0xc0/0xe0 fs/namei.c:4392
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
gadget_subsys.su_mutex --> &opts->dep_lock --> &sb->s_type->i_mutex_key#21

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#21);
lock(&opts->dep_lock);
lock(&sb->s_type->i_mutex_key#21);
lock(gadget_subsys.su_mutex);

*** DEADLOCK ***

3 locks held by syz.0.18/4318:
#0: ffff88801de98460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:386
#1: ffff88805ce19aa0 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
#1: ffff88805ce19aa0 (&default_group_class[depth - 1]#2/1){+.+.}-{3:3}, at: do_rmdir+0x1b0/0x710 fs/namei.c:4205
#2: ffff88805ce1f3f0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
#2: ffff88805ce1f3f0 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: vfs_rmdir+0xe1/0x410 fs/namei.c:4147

stack backtrace:
CPU: 0 PID: 4318 Comm: syz.0.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
check_noncircular+0x296/0x330 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:3788 [inline]
__lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
configfs_rmdir+0x638/0x980 fs/configfs/dir.c:1556
vfs_rmdir+0x19d/0x410 fs/namei.c:4157
do_rmdir+0x27f/0x710 fs/namei.c:4218
__do_sys_unlinkat fs/namei.c:4398 [inline]
__se_sys_unlinkat fs/namei.c:4392 [inline]
__x64_sys_unlinkat+0xc0/0xe0 fs/namei.c:4392
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f21a30fae99
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:00007ffc6e37bc48 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f21a3382fa0 RCX: 00007f21a30fae99
RDX: 0000000000000200 RSI: 0000200000000480 RDI: ffffffffffffff9c
RBP: 00007f21a3190eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f21a3382fac R14: 00007f21a3382fa0 R15: 00007f21a3382fa0
</TASK>


---
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#syz test: git://repo/address.git branch-or-commit-hash
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