possible deadlock in tcm_alloc

Status: upstream: reported on 2026/08/04 18:59
Reported-by: syzbot+9acece748f6cbdfd437f@syzkaller.appspotmail.com
First crash: 1d17h, last: 1d10h
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 possible deadlock in tcm_alloc 4 14 1d10h 1d15h 0/2 upstream: reported on 2026/08/04 20:57
upstream possible deadlock in tcm_alloc prio:low usb 4 syz, C 145 20h13m 3d01h 0/29 upstream: reported C repro on 2026/08/03 10:48
linux-6.1 possible deadlock in tcm_alloc 4 24 1d10h 1d15h 0/3 upstream: reported on 2026/08/04 21:00

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.1/4275 is trying to acquire lock:
ffffffff8cf21328 (tpg_instances_lock){+.+.}-{3:3}, at: tcm_alloc+0x1d/0x1e0 drivers/usb/gadget/function/f_tcm.c:2283

but task is already holding lock:
ffff8881423b9310 (&gi->lock){+.+.}-{3:3}, at: config_usb_cfg_link+0x55/0x250 drivers/usb/gadget/configfs.c:428

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&gi->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
       config_usb_cfg_link+0x55/0x250 drivers/usb/gadget/configfs.c:428
       configfs_symlink+0x5a4/0x13b0 fs/configfs/symlink.c:202
       vfs_symlink+0x245/0x3d0 fs/namei.c:4437
       do_symlinkat+0x1ab/0x6b0 fs/namei.c:4466
       __do_sys_symlinkat fs/namei.c:4483 [inline]
       __se_sys_symlinkat fs/namei.c:4480 [inline]
       __x64_sys_symlinkat+0x95/0xa0 fs/namei.c:4480
       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

-> #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
       usbg_make_tpg+0x144/0x580 drivers/usb/gadget/function/f_tcm.c:1343
       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

-> #0 (tpg_instances_lock){+.+.}-{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
       tcm_alloc+0x1d/0x1e0 drivers/usb/gadget/function/f_tcm.c:2283
       usb_get_function+0x59/0xa0 drivers/usb/gadget/functions.c:61
       config_usb_cfg_link+0x144/0x250 drivers/usb/gadget/configfs.c:458
       configfs_symlink+0x5a4/0x13b0 fs/configfs/symlink.c:202
       vfs_symlink+0x245/0x3d0 fs/namei.c:4437
       do_symlinkat+0x1ab/0x6b0 fs/namei.c:4466
       __do_sys_symlinkat fs/namei.c:4483 [inline]
       __se_sys_symlinkat fs/namei.c:4480 [inline]
       __x64_sys_symlinkat+0x95/0xa0 fs/namei.c:4480
       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:
  tpg_instances_lock --> &sb->s_type->i_mutex_key#21 --> &gi->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&gi->lock);
                               lock(&sb->s_type->i_mutex_key#21);
                               lock(&gi->lock);
  lock(tpg_instances_lock);

 *** DEADLOCK ***

3 locks held by syz.0.1/4275:
 #0: ffff8881465bc460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:386
 #1: ffff8880603eaee0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff8880603eaee0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: configfs_symlink+0x47b/0x13b0 fs/configfs/symlink.c:192
 #2: ffff8881423b9310 (&gi->lock){+.+.}-{3:3}, at: config_usb_cfg_link+0x55/0x250 drivers/usb/gadget/configfs.c:428

stack backtrace:
CPU: 1 PID: 4275 Comm: syz.0.1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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
 tcm_alloc+0x1d/0x1e0 drivers/usb/gadget/function/f_tcm.c:2283
 usb_get_function+0x59/0xa0 drivers/usb/gadget/functions.c:61
 config_usb_cfg_link+0x144/0x250 drivers/usb/gadget/configfs.c:458
 configfs_symlink+0x5a4/0x13b0 fs/configfs/symlink.c:202
 vfs_symlink+0x245/0x3d0 fs/namei.c:4437
 do_symlinkat+0x1ab/0x6b0 fs/namei.c:4466
 __do_sys_symlinkat fs/namei.c:4483 [inline]
 __se_sys_symlinkat fs/namei.c:4480 [inline]
 __x64_sys_symlinkat+0x95/0xa0 fs/namei.c:4480
 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: 0033:0x7f773554f019
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:00007f77337a7028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f77357d6fa0 RCX: 00007f773554f019
RDX: 00002000000009c0 RSI: ffffffffffffff9c RDI: 0000200000000980
RBP: 00007f77355e600c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f77357d7038 R14: 00007f77357d6fa0 R15: 00007ffdd7979728
 </TASK>

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/05 02:06 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/05 02:05 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/05 00:43 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/05 00:42 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/05 00:00 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 23:18 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 23:18 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 22:16 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 22:03 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 22:03 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 19:28 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 19:27 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 19:02 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
2026/08/04 18:59 linux-5.15.y 6e2fd6534337 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in tcm_alloc
* Struck through repros no longer work on HEAD.