WARNING: kobject bug in goku_remove

Status: upstream: reported C repro on 2026/08/13 20:45
Subsystems: kernel
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+06ec7624018233e17113@syzkaller.appspotmail.com
First crash: 20d, last: 10h46m
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
b9f33faa repro-c Reproduced: ✅ WARNING: kobject bug in goku_remove 2026/08/13 11:34 2026/08/13 18:21 2026/08/13 19:07 0165196a
2a51c1fc assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ✅ WARNING: kobject bug in goku_remove 2026/07/26 01:04 2026/07/26 01:04 2026/07/26 01:48 492bab15
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [kernel?] WARNING: kobject bug in goku_remove 0 (1) 2026/08/13 20:45
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/13 20:02 21m nogikh@google.com upstream report job log log

Sample crash report:
usb usb3: USB disconnect, device number 1
uhci_hcd 0000:00:1d.1: USB bus 3 deregistered
------------[ cut here ]------------
kobject: '(null)' (ffff8880281480d8): is not initialized, yet kobject_put() is being called.
WARNING: lib/kobject.c:734 at kobject_put+0x252/0x640 lib/kobject.c:734, CPU#2: syz-executor405/6027
Modules linked in:
CPU: 2 UID: 0 PID: 6027 Comm: syz-executor405 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
RIP: 0010:kobject_put+0x258/0x640 lib/kobject.c:734
Code: 59 f6 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 5e 03 00 00 48 8d 3d 9e 2d 83 05 48 8b 33 48 89 da <67> 48 0f b9 3a e9 0b fe ff ff e8 b9 88 59 f6 be 03 00 00 00 4c 89
RSP: 0018:ffffc90003437728 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff8880281480d8 RCX: ffffffff8bb0e8c4
RDX: ffff8880281480d8 RSI: 0000000000000000 RDI: ffffffff91341850
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888028148114
R13: dffffc0000000000 R14: ffff888028148834 R15: 0000000000000000
FS:  0000555585cdf400(0000) GS:ffff8880d5fe9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe6f14cda8 CR3: 0000000055370000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 put_device+0x1f/0x30 drivers/base/core.c:3880
 goku_remove+0x47/0x470 drivers/usb/gadget/udc/goku_udc.c:1717
 goku_probe+0x2f6/0x3c0 drivers/usb/gadget/udc/goku_udc.c:1830
 local_pci_probe+0xdd/0x1b0 drivers/pci/pci-driver.c:332
 pci_call_probe+0x176/0x800 drivers/pci/pci-driver.c:394
 __pci_device_probe drivers/pci/pci-driver.c:455 [inline]
 pci_device_probe+0x1cd/0x370 drivers/pci/pci-driver.c:489
 call_driver_probe drivers/base/dd.c:628 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:706
 __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
 driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
 __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
 bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
 pci_add_dynid+0x2b5/0x370 drivers/pci/pci-driver.c:77
 new_id_store+0x2a9/0x5b0 drivers/pci/pci-driver.c:249
 drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 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: 0033:0x7f370300ce37
Code: 48 89 fa 4c 89 df e8 98 1d 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff6fddcbc0 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000555585cdf400 RCX: 00007f370300ce37
RDX: 000000000000000d RSI: 00007fff6fddcc80 RDI: 0000000000000003
RBP: 00007fff6fddd400 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 00007fff6fddcf20 R14: 00007fff6fddcd00 R15: 000000000000000a
 </TASK>
----------------
Code disassembly (best guess):
   0:	59                   	pop    %rcx
   1:	f6 48 89 da          	testb  $0xda,-0x77(%rax)
   5:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
   c:	fc ff df
   f:	48 c1 ea 03          	shr    $0x3,%rdx
  13:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
  17:	0f 85 5e 03 00 00    	jne    0x37b
  1d:	48 8d 3d 9e 2d 83 05 	lea    0x5832d9e(%rip),%rdi        # 0x5832dc2
  24:	48 8b 33             	mov    (%rbx),%rsi
  27:	48 89 da             	mov    %rbx,%rdx
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 0b fe ff ff       	jmp    0xfffffe3f
  34:	e8 b9 88 59 f6       	call   0xf65988f2
  39:	be 03 00 00 00       	mov    $0x3,%esi
  3e:	4c                   	rex.WR
  3f:	89                   	.byte 0x89

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/13 20:44 upstream 3aa1dcaa4f6f 4a865b71 .config console log report C ci-qemu-upstream WARNING: kobject bug in goku_remove
2026/07/25 00:57 upstream 48a5a7ab8d6a 4a865b71 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: kobject bug in goku_remove
* Struck through repros no longer work on HEAD.