From: syzbot <syzbot+2799146a53c356f8017d@syzkaller.appspotmail.com>
To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [usb?] possible deadlock in tcm_alloc
Date: Tue, 04 Aug 2026 07:57:23 -0700 [thread overview]
Message-ID: <6a71fdd3.13623e66.bdc14.0017.GAE@google.com> (raw)
In-Reply-To: <6a7071f9.f794c993.27aeb.002f.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: 848acc8ffe1b Merge tag 'fsverity-for-linus' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=176213b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=2799146a53c356f8017d
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=17e5be32580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17639bb9580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-848acc8f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6fb497cc0c8d/vmlinux-848acc8f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/663ccee34982/bzImage-848acc8f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2799146a53c356f8017d@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/5925 is trying to acquire lock:
ffffffff90253240 (tpg_instances_lock){+.+.}-{4:4}, at: tcm_alloc+0x20/0x440 drivers/usb/gadget/function/f_tcm.c:2733
but task is already holding lock:
ffff88802e43c390 (&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_mkdirat fs/namei.c:5330 [inline]
__se_sys_mkdirat fs/namei.c:5327 [inline]
__x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5327
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_mkdirat fs/namei.c:5330 [inline]
__se_sys_mkdirat fs/namei.c:5327 [inline]
__x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5327
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.0.17/5925:
#0: ffff888023820450 (sb_writers#13){.+.+}-{0:0}, at: filename_create+0x10d/0x400 fs/namei.c:4948
#1: ffff8880403dac00 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
#1: ffff8880403dac00 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: configfs_symlink+0x3c0/0x11f0 fs/configfs/symlink.c:186
#2: ffff88802e43c390 (&gi->lock){+.+.}-{4:4}, at: config_usb_cfg_link+0x57/0x3a0 drivers/usb/gadget/configfs.c:439
stack backtrace:
CPU: 1 UID: 0 PID: 5925 Comm: syz.0.17 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: 0033:0x7f71ccb9e019
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:00007ffc4ccd6728 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f71cce25fa0 RCX: 00007f71ccb9e019
RDX: 00002000000009c0 RSI: ffffffffffffff9c RDI: 0000200000000980
RBP: 00007f71ccc3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f71cce25fac R14: 00007f71cce25fa0 R15: 00007f71cce25fa0
</TASK>
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
prev parent reply other threads:[~2026-08-04 14:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-03 10:48 [syzbot] [usb?] possible deadlock in tcm_alloc syzbot
2026-08-04 14:57 ` syzbot [this message]
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