[syzbot] [mm?] WARNING in __put_task_struct (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2b7a25df823d Merge tag 'mm-nonmm-stable-2026-02-18-19-56' ..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=14573b3a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1ff39736314a9939
dashboard link: https://syzkaller.appspot.com/bug?extid=c978a74d4872e06c4928
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/10a06102f92f/disk-2b7a25df.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cb322de10b94/vmlinux-2b7a25df.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7a3e5e026b94/bzImage-2b7a25df.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c978a7...@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_read(&tsk->usage)
WARNING: kernel/fork.c:779 at __put_task_struct+0x33c/0x400 kernel/fork.c:779, CPU#1: kworker/1:6/5227
Modules linked in:
CPU: 1 UID: 0 PID: 5227 Comm: kworker/1:6 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: usb_hub_wq hub_event
RIP: 0010:__put_task_struct+0x33c/0x400 kernel/fork.c:779
Code: 4c 89 e6 e8 b6 7e 98 00 e9 f2 fe ff ff e8 fc 7a 3d 00 be 03 00 00 00 4c 89 e7 e8 1f a0 57 01 e9 db fe ff ff e8 e5 7a 3d 00 90 <0f> 0b 90 e8 dc 7a 3d 00 65 48 3b 1d 4c 94 80 0b 0f 85 64 fd ff ff
RSP: 0018:ffffc900001a8e00 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88811283d700 RCX: ffffffff8174391b
RDX: ffff88811956ba00 RSI: ffffffff81743bbb RDI: ffff88811956ba00
RBP: 00000000c0000000 R08: 0000000000000005 R09: 0000000000000000
R10: 00000000c0000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff88811956ba00 R14: ffffffff81984efd R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8882687d3000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe6af2e9d40 CR3: 00000001195d8000 CR4: 00000000003506f0
Call Trace:
<IRQ>
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2869
handle_softirqs+0x1de/0x9d0 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0xed/0x150 kernel/softirq.c:723
irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
sysvec_apic_timer_interrupt+0x8f/0xb0 arch/x86/kernel/apic/apic.c:1056
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:console_flush_one_record+0xac3/0xe50 kernel/printk/printk.c:3270
Code: 00 e8 51 5a 28 00 9c 5d 81 e5 00 02 00 00 31 ff 48 89 ee e8 5f 62 20 00 48 85 ed 0f 85 d7 01 00 00 e8 71 67 20 00 fb 4c 89 e8 <48> c1 e8 03 42 80 3c 38 00 0f 85 64 03 00 00 48 8b 0c 24 48 8b 6b
RSP: 0018:ffffc9000362ea68 EFLAGS: 00000283
RAX: ffffffff89c75f58 RBX: ffffffff89c75f00 RCX: ffffc90012887000
RDX: 0000000000100000 RSI: ffffffff81914f2f RDI: ffff88811956ba00
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000012857
R13: ffffffff89c75f58 R14: ffffc9000362eae8 R15: dffffc0000000000
console_flush_all kernel/printk/printk.c:3343 [inline]
__console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
console_unlock+0x103/0x260 kernel/printk/printk.c:3413
vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
__warn_printf lib/bug.c:190 [inline]
__report_bug.cold+0x7b/0x137 lib/bug.c:244
report_bug_entry+0xe1/0x290 lib/bug.c:269
handle_bug+0x1c9/0x2a0 arch/x86/kernel/traps.c:430
exc_invalid_op+0x17/0x50 arch/x86/kernel/traps.c:489
asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
RIP: 0010:refcount_warn_saturate+0x111/0x130 lib/refcount.c:25
Code: cc e8 e3 d9 e5 fe 48 8d 3d 4c 70 28 08 67 48 0f b9 3a e8 d2 d9 e5 fe 5b 5d e9 cb 6d 9f 04 e8 c6 d9 e5 fe 48 8d 3d 3f 70 28 08 <67> 48 0f b9 3a e8 b5 d9 e5 fe 5b 5d c3 cc cc cc cc 48 89 df e8 46
RSP: 0018:ffffc9000362ef30 EFLAGS: 00010283
RAX: 00000000000428c1 RBX: ffff88811283d728 RCX: ffffc90012887000
RDX: 0000000000100000 RSI: ffffffff82cbdcda RDI: ffffffff8af44d20
RBP: 0000000000000002 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000002 R11: ffff8881f5739708 R12: ffff88810cf18000
R13: ffff88811283d728 R14: 0000000000000001 R15: 0000000000000001
__refcount_add include/linux/refcount.h:289 [inline]
__refcount_inc include/linux/refcount.h:366 [inline]
refcount_inc include/linux/refcount.h:383 [inline]
get_task_struct include/linux/sched/task.h:116 [inline]
kthread_stop+0x602/0x680 kernel/kthread.c:786
rsi_kill_thread drivers/net/wireless/rsi/rsi_common.h:78 [inline]
rsi_91x_deinit+0x102/0x1f0 drivers/net/wireless/rsi/rsi_91x_main.c:405
rsi_probe+0xd27/0x1aa0 drivers/net/wireless/rsi/rsi_91x_usb.c:861
usb_probe_interface+0x303/0x8f0 drivers/usb/core/driver.c:396
call_driver_probe drivers/base/dd.c:583 [inline]
really_probe+0x241/0xa60 drivers/base/dd.c:661
__driver_probe_device+0x1de/0x400 drivers/base/dd.c:803
driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:833
__device_attach_driver+0x1ff/0x3e0 drivers/base/dd.c:961
bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
__device_attach+0x1e4/0x4d0 drivers/base/dd.c:1033
device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1088
bus_probe_device+0x64/0x160 drivers/base/bus.c:574
device_add+0x11d9/0x1950 drivers/base/core.c:3689
usb_set_configuration+0xd97/0x1c60 drivers/usb/core/message.c:2210
usb_generic_driver_probe+0xa1/0xe0 drivers/usb/core/generic.c:250
usb_probe_device+0xef/0x400 drivers/usb/core/driver.c:291
call_driver_probe drivers/base/dd.c:583 [inline]
really_probe+0x241/0xa60 drivers/base/dd.c:661
__driver_probe_device+0x1de/0x400 drivers/base/dd.c:803
driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:833
__device_attach_driver+0x1ff/0x3e0 drivers/base/dd.c:961
bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
__device_attach+0x1e4/0x4d0 drivers/base/dd.c:1033
device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1088
bus_probe_device+0x64/0x160 drivers/base/bus.c:574
device_add+0x11d9/0x1950 drivers/base/core.c:3689
usb_new_device.cold+0x685/0x115c drivers/usb/core/hub.c:2695
hub_port_connect drivers/usb/core/hub.c:5567 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
port_event drivers/usb/core/hub.c:5871 [inline]
hub_event+0x314d/0x4af0 drivers/usb/core/hub.c:5953
process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
process_scheduled_works kernel/workqueue.c:3358 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
kthread+0x370/0x450 kernel/kthread.c:467
ret_from_fork+0x6c3/0xcb0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
----------------
Code disassembly (best guess):
0: 00 e8 add %ch,%al
2: 51 push %rcx
3: 5a pop %rdx
4: 28 00 sub %al,(%rax)
6: 9c pushf
7: 5d pop %rbp
8: 81 e5 00 02 00 00 and $0x200,%ebp
e: 31 ff xor %edi,%edi
10: 48 89 ee mov %rbp,%rsi
13: e8 5f 62 20 00 call 0x206277
18: 48 85 ed test %rbp,%rbp
1b: 0f 85 d7 01 00 00 jne 0x1f8
21: e8 71 67 20 00 call 0x206797
26: fb sti
27: 4c 89 e8 mov %r13,%rax
* 2a: 48 c1 e8 03 shr $0x3,%rax <-- trapping instruction
2e: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
33: 0f 85 64 03 00 00 jne 0x39d
39: 48 8b 0c 24 mov (%rsp),%rcx
3d: 48 rex.W
3e: 8b .byte 0x8b
3f: 6b .byte 0x6b


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