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BUG: KASAN: use-after-free in netdev_need_ops_lock include/net/netdev_lock.h:30 [inline]
BUG: KASAN: use-after-free in netdev_unlock_ops include/net/netdev_lock.h:47 [inline]
BUG: KASAN: use-after-free in __linkwatch_run_queue+0x6a0/0x7f0 net/core/link_watch.c:245
Read of size 1 at addr ffff88807b680cc9 by task kworker/u8:10/3017

CPU: 0 UID: 0 PID: 3017 Comm: kworker/u8:10 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Workqueue: events_unbound linkwatch_event
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 netdev_need_ops_lock include/net/netdev_lock.h:30 [inline]
 netdev_unlock_ops include/net/netdev_lock.h:47 [inline]
 __linkwatch_run_queue+0x6a0/0x7f0 net/core/link_watch.c:245
 linkwatch_event+0x4c/0x60 net/core/link_watch.c:304
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340
 worker_thread+0xda6/0x1360 kernel/workqueue.c:3421
 kthread+0x726/0x8b0 kernel/kthread.c:463
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807b6816c0 pfn:0x7b680
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00015a5908 ffff8880b8640c00 0000000000000000
raw: ffff88807b6816c0 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x446dc0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_COMP), pid 19386, tgid 19378 (syz.4.3587), ts 963179944746, free_ts 963871329296
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 ___kmalloc_large_node+0x4e/0x150 mm/slub.c:5598
 __kmalloc_large_node_noprof+0x18/0x90 mm/slub.c:5629
 __do_kmalloc_node mm/slub.c:5645 [inline]
 __kvmalloc_node_noprof+0x6e/0x8d0 mm/slub.c:7140
 alloc_netdev_mqs+0xa6/0x11b0 net/core/dev.c:12012
 tun_set_iff+0x532/0xf00 drivers/net/tun.c:2778
 __tun_chr_ioctl+0x7bb/0x1e10 drivers/net/tun.c:3088
 __do_compat_sys_ioctl fs/ioctl.c:695 [inline]
 __se_compat_sys_ioctl fs/ioctl.c:638 [inline]
 __ia32_compat_sys_ioctl+0x5ea/0x950 fs/ioctl.c:638
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x1d2/0x540 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
page last free pid 19378 tgid 19378 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xbf8/0xd70 mm/page_alloc.c:2973
 device_release+0x9e/0x1d0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x228/0x560 lib/kobject.c:737
 netdev_run_todo+0xc75/0xde0 net/core/dev.c:11713
 tun_detach drivers/net/tun.c:640 [inline]
 tun_chr_close+0x13c/0x1c0 drivers/net/tun.c:3436
 __fput+0x44f/0xa70 fs/file_table.c:468
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 __do_fast_syscall_32+0x38e/0x540 arch/x86/entry/syscall_32.c:310
 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Memory state around the buggy address:
 ffff88807b680b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807b680c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807b680c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88807b680d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807b680d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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