==================================================================
BUG: KASAN: use-after-free in netdev_need_ops_lock include/net/netdev_lock.h:33 [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+0x880/0x8a0 net/core/link_watch.c:245
Read of size 8 at addr ffff88802a504008 by task kworker/u32:0/12

CPU: 1 UID: 0 PID: 12 Comm: kworker/u32:0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_unbound linkwatch_event
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 netdev_need_ops_lock include/net/netdev_lock.h:33 [inline]
 netdev_unlock_ops include/net/netdev_lock.h:47 [inline]
 __linkwatch_run_queue+0x880/0x8a0 net/core/link_watch.c:245
 linkwatch_event+0x8f/0xc0 net/core/link_watch.c:304
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88802a505e00 pfn:0x2a504
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea000092a008 ffff88802b440700 0000000000000000
raw: ffff88802a505e00 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 20191, tgid 20187 (syz.0.3066), ts 1040095098210, free_ts 1041021394924
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1af/0x220 mm/page_alloc.c:1845
 prep_new_page mm/page_alloc.c:1853 [inline]
 get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3879
 __alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5178
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
 ___kmalloc_large_node+0xed/0x160 mm/slub.c:5591
 __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:5622
 __do_kmalloc_node mm/slub.c:5638 [inline]
 __kvmalloc_node_noprof.cold+0xf/0x66 mm/slub.c:7112
 alloc_netdev_mqs+0xd7/0x1550 net/core/dev.c:11900
 tun_set_iff drivers/net/tun.c:2778 [inline]
 __tun_chr_ioctl+0x193e/0x4880 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+0x242/0x370 fs/ioctl.c:638
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x7c/0x300 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:331
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
page last free pid 20187 tgid 20187 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2901
 device_release+0xa4/0x240 drivers/base/core.c:2565
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1e7/0x5a0 lib/kobject.c:737
 netdev_run_todo+0x7e9/0x1320 net/core/dev.c:11601
 tun_detach drivers/net/tun.c:640 [inline]
 tun_chr_close+0xea/0x230 drivers/net/tun.c:3436
 __fput+0x402/0xb70 fs/file_table.c:468
 task_work_run+0x150/0x240 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x130 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 __do_fast_syscall_32+0x240/0x300 arch/x86/entry/syscall_32.c:309
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:331
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Memory state around the buggy address:
 ffff88802a503f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802a503f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802a504000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88802a504080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88802a504100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================