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BUG: KASAN: use-after-free in con_shutdown+0x85/0x90 drivers/tty/vt/vt.c:2930
Write of size 8 at addr ffff888099022d08 by task syz-executor.4/16798

CPU: 0 PID: 16798 Comm: syz-executor.4 Not tainted 4.14.158-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x142/0x197 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
 con_shutdown+0x85/0x90 drivers/tty/vt/vt.c:2930
 release_tty+0xbf/0x7c0 drivers/tty/tty_io.c:1501
 tty_release_struct+0x3c/0x50 drivers/tty/tty_io.c:1616
 tty_release+0xaa3/0xd60 drivers/tty/tty_io.c:1776
 __fput+0x275/0x7a0 fs/file_table.c:210
 ____fput+0x16/0x20 fs/file_table.c:244
 task_work_run+0x114/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x7be/0x2c80 kernel/exit.c:854
 do_group_exit+0x111/0x330 kernel/exit.c:951
 get_signal+0x381/0x1cd0 kernel/signal.c:2413
 do_signal+0x86/0x19a0 arch/x86/kernel/signal.c:814
 exit_to_usermode_loop+0x15c/0x220 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath+0x29e/0x330 arch/x86/entry/common.c:270
 ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:397
RIP: 0033:0x45d049
RSP: 002b:00007f4ac1bc3db0 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: 0000000000000000 RBX: 00007f4ac1bc4700 RCX: 000000000045d049
RDX: 00007f4ac1bc49d0 RSI: 00007f4ac1bc3db0 RDI: 00000000003d0f00
RBP: 00007ffc78f80720 R08: 00007f4ac1bc4700 R09: 00007f4ac1bc4700
R10: 00007f4ac1bc49d0 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffc78f805bf R14: 00007f4ac1bc49c0 R15: 000000000075bfd4

Allocated by task 16788:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 kmem_cache_alloc_trace+0x152/0x790 mm/slab.c:3618
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 vc_allocate drivers/tty/vt/vt.c:772 [inline]
 vc_allocate+0x148/0x580 drivers/tty/vt/vt.c:753
 con_install+0x52/0x400 drivers/tty/vt/vt.c:2881
 tty_driver_install_tty drivers/tty/tty_io.c:1225 [inline]
 tty_init_dev drivers/tty/tty_io.c:1338 [inline]
 tty_init_dev+0xea/0x3a0 drivers/tty/tty_io.c:1315
 tty_open_by_driver drivers/tty/tty_io.c:1973 [inline]
 tty_open+0x414/0xa10 drivers/tty/tty_io.c:2021
 chrdev_open+0x207/0x590 fs/char_dev.c:423
 do_dentry_open+0x73b/0xeb0 fs/open.c:777
 vfs_open+0x105/0x220 fs/open.c:891
 do_last fs/namei.c:3425 [inline]
 path_openat+0x8bd/0x3f70 fs/namei.c:3566
 do_filp_open+0x18e/0x250 fs/namei.c:3600
 do_sys_open+0x2c5/0x430 fs/open.c:1084
 SYSC_open fs/open.c:1102 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1097
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 16800:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 vt_disallocate_all+0x286/0x380 drivers/tty/vt/vt_ioctl.c:323
 vt_ioctl+0x76b/0x2170 drivers/tty/vt/vt_ioctl.c:816
 tty_ioctl+0x841/0x1320 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff888099022c00
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 264 bytes inside of
 2048-byte region [ffff888099022c00, ffff888099023400)
The buggy address belongs to the page:
page:ffffea0002640880 count:1 mapcount:0 mapping:ffff888099022380 index:0xffff888099023480 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff888099022380 ffff888099023480 0000000100000002
raw: ffffea00017fe8a0 ffffea00015fc1a0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888099022c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888099022c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888099022d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff888099022d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888099022e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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