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BUG: KASAN: use-after-free in con_shutdown+0x7f/0x90 drivers/tty/vt/vt.c:2930
Write of size 8 at addr ffff88805ba7f488 by task syz-executor.3/9549

CPU: 1 PID: 9549 Comm: syz-executor.3 Not tainted 4.14.172-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+0x13e/0x194 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1e2 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+0xa9/0x2ae mm/kasan/report.c:393
 con_shutdown+0x7f/0x90 drivers/tty/vt/vt.c:2930
 release_tty+0xb6/0x7a0 drivers/tty/tty_io.c:1501
 tty_release_struct+0x37/0x50 drivers/tty/tty_io.c:1616
 tty_release+0xaa6/0xd60 drivers/tty/tty_io.c:1776
 __fput+0x25f/0x790 fs/file_table.c:210
 task_work_run+0x113/0x190 kernel/task_work.c:113
 get_signal+0x187f/0x1ca0 kernel/signal.c:2229
 do_signal+0x7c/0x1690 arch/x86/kernel/signal.c:814
 exit_to_usermode_loop+0x159/0x220 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c4a9
RSP: 002b:00007fc8f1d9bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007fc8f1d9c6d4 RCX: 000000000045c4a9
RDX: 0000000020000040 RSI: 0000000000005423 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000583 R14: 00000000004c7ddd R15: 000000000076bf2c

Allocated by task 382:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:529
 kmem_cache_alloc_trace+0x14d/0x7b0 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+0x142/0x550 drivers/tty/vt/vt.c:753
 con_install+0x4f/0x3e0 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+0xe1/0x3a0 drivers/tty/tty_io.c:1315
 tty_open_by_driver drivers/tty/tty_io.c:1973 [inline]
 tty_open+0x410/0x9c0 drivers/tty/tty_io.c:2021
 chrdev_open+0x1fc/0x540 fs/char_dev.c:423
 do_dentry_open+0x732/0xe90 fs/open.c:777
 vfs_open+0x105/0x220 fs/open.c:891
 do_last fs/namei.c:3428 [inline]
 path_openat+0x8ca/0x3c50 fs/namei.c:3569
 do_filp_open+0x18e/0x250 fs/namei.c:3603
 do_sys_open+0x29d/0x3f0 fs/open.c:1084
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 9587:
 save_stack+0x32/0xa0 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+0xcb/0x260 mm/slab.c:3815
 vt_disallocate_all+0x25c/0x340 drivers/tty/vt/vt_ioctl.c:323
 vt_ioctl+0x6e3/0x1f00 drivers/tty/vt/vt_ioctl.c:816
 tty_ioctl+0x6c5/0x1220 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff88805ba7f380
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 264 bytes inside of
 2048-byte region [ffff88805ba7f380, ffff88805ba7fb80)
The buggy address belongs to the page:
page:ffffea00016e9f80 count:1 mapcount:0 mapping:ffff88805ba7e280 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88805ba7e280 0000000000000000 0000000100000003
raw: ffffea00026ce2a0 ffffea0002407320 ffff88812fe56c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88805ba7f380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805ba7f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805ba7f480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88805ba7f500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805ba7f580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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