[syzbot] [net?] KASAN: use-after-free Read in __linkwatch_run_queue

[syzbot <syzbot+1ec2f6a450f0b54af8c8@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    9f35e33144ae x86/its: Fix build errors when CONFIG_MODULES=n
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=107f56f4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c9b33a466dfee330
dashboard link: https://syzkaller.appspot.com/bug?extid=1ec2f6a450f0b54af8c8
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/136b6fd9c02c/disk-9f35e331.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1db87e48df97/vmlinux-9f35e331.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9588fd34964c/bzImage-9f35e331.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1ec2f6a450f0b54af8c8@syzkaller.appspotmail.com

==================================================================
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+0x7d8/0x8a0 net/core/link_watch.c:245
Read of size 8 at addr ffff88807a5ecb88 by task kworker/u8:9/6112

CPU: 0 UID: 0 PID: 6112 Comm: kworker/u8:9 Not tainted 6.15.0-rc6-syzkaller-00052-g9f35e33144ae #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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:408 [inline]
 print_report+0xc3/0x670 mm/kasan/report.c:521
 kasan_report+0xe0/0x110 mm/kasan/report.c:634
 netdev_need_ops_lock include/net/netdev_lock.h:30 [inline]
 netdev_unlock_ops include/net/netdev_lock.h:47 [inline]
 __linkwatch_run_queue+0x7d8/0x8a0 net/core/link_watch.c:245
 linkwatch_event+0x8f/0xc0 net/core/link_watch.c:304
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 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:0xffff88807a5efc00 pfn:0x7a5ec
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001aedf08 ffff8880b853fa00 0000000000000000
raw: ffff88807a5efc00 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 13363, tgid 13353 (syz.0.2160), ts 637147906784, free_ts 639281975158
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1718
 prep_new_page mm/page_alloc.c:1726 [inline]
 get_page_from_freelist+0x135c/0x3920 mm/page_alloc.c:3688
 __alloc_frozen_pages_noprof+0x263/0x23a0 mm/page_alloc.c:4970
 __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:5004
 __alloc_pages_node_noprof include/linux/gfp.h:284 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:311 [inline]
 ___kmalloc_large_node+0x82/0x1e0 mm/slub.c:4271
 __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:4299
 __do_kmalloc_node mm/slub.c:4315 [inline]
 __kvmalloc_node_noprof.cold+0xb/0x65 mm/slub.c:5012
 alloc_netdev_mqs+0xd2/0x1570 net/core/dev.c:11604
 tun_set_iff drivers/net/tun.c:2752 [inline]
 __tun_chr_ioctl+0x1964/0x4740 drivers/net/tun.c:3048
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 13353 tgid 13353 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 __free_frozen_pages+0x69d/0xff0 mm/page_alloc.c:2725
 __folio_put+0x329/0x450 mm/swap.c:112
 device_release+0xa4/0x240 drivers/base/core.c:2568
 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:11305
 tun_detach drivers/net/tun.c:639 [inline]
 tun_chr_close+0xea/0x230 drivers/net/tun.c:3390
 __fput+0x402/0xb70 fs/file_table.c:465
 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 kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218
 do_syscall_64+0xda/0x260 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88807a5eca80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807a5ecb00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807a5ecb80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88807a5ecc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807a5ecc80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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