==================================================================
BUG: KASAN: slab-use-after-free in stop_t
BUG: KASAN: slab-use-after-free in __stop_tty drivers/tty/tty_io.c:742 [inline]
BUG: KASAN: slab-use-after-free in stop_tty+0xec/0x110 drivers/tty/tty_io.c:766
Read of size 1 at addr ffff88806135f480 by task syz.3.1293/11621

CPU: 0 UID: 0 PID: 11621 Comm: syz.3.1293 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 __stop_tty drivers/tty/tty_io.c:742 [inline]
 stop_tty+0xec/0x110 drivers/tty/tty_io.c:766
 kbd_keycode drivers/tty/vt/keyboard.c:1574 [inline]
 kbd_event+0x2e8d/0x41f0 drivers/tty/vt/keyboard.c:1592
 input_handle_events_default+0xd4/0x1a0 drivers/input/input.c:2614
 input_pass_values+0x288/0x890 drivers/input/input.c:128
 input_event_dispose+0x35f/0x700 drivers/input/input.c:342
 input_inject_event+0x1fa/0x310 drivers/input/input.c:424
 evdev_write+0x328/0x4c0 drivers/input/evdev.c:533
 vfs_write+0x29f/0xbb0 fs/read_write.c:685
 ksys_write+0x156/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc530a8e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc52ece6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc530d15fa0 RCX: 00007fc530a8e159
RDX: 0000000000002250 RSI: 0000200000000040 RDI: 0000000000000007
RBP: 00007fc530b25024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc530d16038 R14: 00007fc530d15fa0 R15: 00007ffd751a7478
 </TASK>

Allocated by task 11621:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3d5/0x680 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 alloc_tty_struct+0xa6/0x7a0 drivers/tty/tty_io.c:3075
 tty_init_dev+0x59/0x4d0 drivers/tty/tty_io.c:1373
 tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 tty_open+0x7e5/0xcd0 drivers/tty/tty_io.c:2093
 chrdev_open+0x4dc/0x600 fs/char_dev.c:411
 do_dentry_open+0x849/0x1420 fs/open.c:996
 vfs_open+0x3b/0x350 fs/open.c:1101
 do_open fs/namei.c:4837 [inline]
 path_openat+0x1448/0x1d60 fs/namei.c:5000
 do_file_open+0x23e/0x4a0 fs/namei.c:5029
 do_sys_openat2+0x115/0x200 fs/open.c:1417
 do_sys_open fs/open.c:1423 [inline]
 __do_sys_openat fs/open.c:1439 [inline]
 __se_sys_openat fs/open.c:1434 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1434
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5699:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6499 [inline]
 kfree+0x1c5/0x6d0 mm/slub.c:6792
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 insert_work+0x3d/0x330 kernel/workqueue.c:2272
 __queue_work+0xd4b/0x1120 kernel/workqueue.c:2448
 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2501
 tty_release_struct+0xb8/0xd0 drivers/tty/tty_io.c:1665
 tty_release+0xc6b/0x1680 drivers/tty/tty_io.c:1825
 __fput+0x42a/0xa80 fs/file_table.c:512
 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:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88806135f000
 which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 1152 bytes inside of
 freed 2048-byte region [ffff88806135f000, ffff88806135f800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x61358
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888061358811
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ff053c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000300080008 00000000f5000000 ffff888061358811
head: 0080000000000040 ffff88813ff053c0 dead000000000100 dead000000000122
head: 0000000000000000 0000000300080008 00000000f5000000 ffff888061358811
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5960, tgid 5960 (syz-executor), ts 198319865497
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x2591/0x2600 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x230/0x5c0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab+0x7d/0x620 mm/slub.c:3462
 new_slab mm/slub.c:3513 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7410
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x339/0x690 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_node_track_caller_noprof+0x61e/0x7b0 mm/slub.c:5545
 kmemdup_noprof+0x2b/0x70 mm/util.c:138
 kmemdup_noprof include/linux/fortify-string.h:715 [inline]
 neigh_sysctl_register+0xae/0xa90 net/core/neighbour.c:3854
 addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7396
 ipv6_add_dev+0xd64/0x1400 net/ipv6/addrconf.c:460
 addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3686
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2313 [inline]
 call_netdevice_notifiers net/core/dev.c:2327 [inline]
 register_netdevice+0x18c0/0x1ed0 net/core/dev.c:11541
 veth_newlink+0x4d7/0xdd0 drivers/net/veth.c:1870
 rtnl_newlink_create+0x305/0x7b0 net/core/rtnetlink.c:3969
page last free pid 5934 tgid 5934 ts 184998146825 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 free_pages_prepare+0x9c6/0xac0 mm/page_alloc.c:1463
 __free_contig_range_common+0x174/0x340 mm/page_alloc.c:7072
 __free_contig_range mm/page_alloc.c:7117 [inline]
 free_pages_bulk+0x48/0x120 mm/page_alloc.c:5322
 vm_area_free_pages mm/vmalloc.c:3461 [inline]
 vfree+0x278/0x500 mm/vmalloc.c:3510
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3414
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88806135f380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806135f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806135f480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88806135f500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806135f580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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