possible deadlock in tcm_alloc

Status: upstream: reported on 2026/08/03 10:48
Subsystems: usb
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+2799146a53c356f8017d@syzkaller.appspotmail.com
First crash: 4d09h, last: 4d08h
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
faf7ef40 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ possible deadlock in tcm_alloc 2026/08/01 00:05 2026/08/01 00:05 2026/08/01 00:09 7664cf44 

			
				
	

	
	



			

		

	

	
	

		

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			[syzbot] [usb?] possible deadlock in tcm_alloc
			0 (1)
			2026/08/03 10:48
		

	
	




			
			
		

	

	

	
	
Sample crash report:

	
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.239/6703 is trying to acquire lock:
ffffffff90252b60 (tpg_instances_lock){+.+.}-{4:4}, at: tcm_alloc+0x20/0x440 drivers/usb/gadget/function/f_tcm.c:2733

but task is already holding lock:
ffff888058a66390 (&gi->lock){+.+.}-{4:4}, at: config_usb_cfg_link+0x57/0x3a0 drivers/usb/gadget/configfs.c:439

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&gi->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
       config_usb_cfg_link+0x57/0x3a0 drivers/usb/gadget/configfs.c:439
       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]
       __x64_sys_symlinkat+0x9c/0xe0 fs/namei.c:5700
       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

-> #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
       usbg_make_tpg+0x1a4/0x620 drivers/usb/gadget/function/f_tcm.c:1678
       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

-> #0 (tpg_instances_lock){+.+.}-{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
       tcm_alloc+0x20/0x440 drivers/usb/gadget/function/f_tcm.c:2733
       usb_get_function+0x5e/0xd0 drivers/usb/gadget/functions.c:61
       config_usb_cfg_link+0x1ed/0x3a0 drivers/usb/gadget/configfs.c:469
       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]
       __x64_sys_symlinkat+0x9c/0xe0 fs/namei.c:5700
       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:
  tpg_instances_lock --> &sb->s_type->i_mutex_key#24 --> &gi->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&gi->lock);
                               lock(&sb->s_type->i_mutex_key#24);
                               lock(&gi->lock);
  lock(tpg_instances_lock);

 *** DEADLOCK ***

3 locks held by syz.0.239/6703:
 #0: ffff888024522450 (sb_writers#13){.+.+}-{0:0}, at: filename_create+0x10d/0x400 fs/namei.c:4948
 #1: ffff888057d20ac0 (&sb->s_type->i_mutex_key#24){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #1: ffff888057d20ac0 (&sb->s_type->i_mutex_key#24){++++}-{4:4}, at: configfs_symlink+0x3c0/0x11f0 fs/configfs/symlink.c:186
 #2: ffff888058a66390 (&gi->lock){+.+.}-{4:4}, at: config_usb_cfg_link+0x57/0x3a0 drivers/usb/gadget/configfs.c:439

stack backtrace:
CPU: 2 UID: 0 PID: 6703 Comm: syz.0.239 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
 tcm_alloc+0x20/0x440 drivers/usb/gadget/function/f_tcm.c:2733
 usb_get_function+0x5e/0xd0 drivers/usb/gadget/functions.c:61
 config_usb_cfg_link+0x1ed/0x3a0 drivers/usb/gadget/configfs.c:469
 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]
 __x64_sys_symlinkat+0x9c/0xe0 fs/namei.c:5700
 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: 0033:0x7f358b59df99
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:00007f358c541028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f358b825fa0 RCX: 00007f358b59df99
RDX: 0000200000000400 RSI: ffffffffffffff9c RDI: 0000200000000300
RBP: 00007f358b634ec4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f358b826038 R14: 00007f358b825fa0 R15: 00007ffdf9fc7e88
 </TASK>



	

	



	Crashes (4):
		
		

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			2026/07/30 11:16
			upstream
			11028ab62899
			abc81b93
			.config
			console log
			report
			
			
			info
			
				[disk image (non-bootable)]
			
				[vmlinux]
			
				[kernel image]
			
			ci-qemu-upstream
			possible deadlock in tcm_alloc
		

		
		

			2026/07/30 10:39
			upstream
			11028ab62899
			abc81b93
			.config
			console log
			report
			
			
			info
			
				[disk image (non-bootable)]
			
				[vmlinux]
			
				[kernel image]
			
			ci-qemu-upstream
			possible deadlock in tcm_alloc
		

		
		

			2026/07/30 10:39
			upstream
			11028ab62899
			abc81b93
			.config
			console log
			report
			
			
			info
			
				[disk image (non-bootable)]
			
				[vmlinux]
			
				[kernel image]
			
			ci-qemu-upstream
			possible deadlock in tcm_alloc
		

		
		

			2026/07/30 10:38
			upstream
			11028ab62899
			abc81b93
			.config
			console log
			report
			
			
			info
			
				[disk image (non-bootable)]
			
				[vmlinux]
			
				[kernel image]
			
			ci-qemu-upstream
			possible deadlock in tcm_alloc
		

		
		


* Struck through repros no longer work on HEAD.