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2002:a05:6820:8587:20b0:6a1:963d:a040 with SMTP id 006d021491bc7-6ae4319060amr14332716eaf.2.1785855443228; Tue, 04 Aug 2026 07:57:23 -0700 (PDT) Date: Tue, 04 Aug 2026 07:57:23 -0700 In-Reply-To: <6a7071f9.f794c993.27aeb.002f.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a71fdd3.13623e66.bdc14.0017.GAE@google.com> Subject: Re: [syzbot] [usb?] possible deadlock in tcm_alloc From: syzbot To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" 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: __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 --- 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.