==================================================================
BUG: KASAN: use-after-free in con_shutdown+0x7f/0x90 drivers/tty/vt/vt.c:3287
Write of size 8 at addr ffff8880a21ec108 by task syz-executor.5/9166

CPU: 1 PID: 9166 Comm: syz-executor.5 Not tainted 5.6.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
 __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:506
 kasan_report+0xe/0x20 mm/kasan/common.c:641
 con_shutdown+0x7f/0x90 drivers/tty/vt/vt.c:3287
 release_tty+0xca/0x450 drivers/tty/tty_io.c:1514
 tty_release_struct+0x37/0x50 drivers/tty/tty_io.c:1629
 tty_release+0xbc7/0xe90 drivers/tty/tty_io.c:1789
 __fput+0x2da/0x850 fs/file_table.c:280
 task_work_run+0x13f/0x1b0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x416041
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffd6b26ecd0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000416041
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 0000000000000001 R08: ffffffff8100975e R09: 00000000ec0c4446
R10: 00007ffd6b26edb0 R11: 0000000000000293 R12: 000000000076c920
R13: 000000000076c920 R14: 0000000000254952 R15: 000000000076bfcc

Allocated by task 9223:
 save_stack+0x1b/0x80 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:515 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 vc_allocate drivers/tty/vt/vt.c:1096 [inline]
 vc_allocate+0x1e2/0x6e0 drivers/tty/vt/vt.c:1077
 con_install+0x4f/0x400 drivers/tty/vt/vt.c:3238
 tty_driver_install_tty drivers/tty/tty_io.c:1228 [inline]
 tty_init_dev drivers/tty/tty_io.c:1341 [inline]
 tty_init_dev+0xf5/0x460 drivers/tty/tty_io.c:1318
 tty_open_by_driver drivers/tty/tty_io.c:1987 [inline]
 tty_open+0x47f/0xb30 drivers/tty/tty_io.c:2035
 chrdev_open+0x219/0x5c0 fs/char_dev.c:414
 do_dentry_open+0x4a2/0x1250 fs/open.c:797
 do_last fs/namei.c:3490 [inline]
 path_openat+0x122a/0x32b0 fs/namei.c:3607
 do_filp_open+0x192/0x260 fs/namei.c:3637
 do_sys_openat2+0x54c/0x740 fs/open.c:1149
 do_sys_open+0xc3/0x140 fs/open.c:1165
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9346:
 save_stack+0x1b/0x80 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:476
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 vt_disallocate_all+0x293/0x3b0 drivers/tty/vt/vt_ioctl.c:323
 vt_ioctl+0xb79/0x2470 drivers/tty/vt/vt_ioctl.c:816
 tty_ioctl+0xedd/0x1440 drivers/tty/tty_io.c:2660
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a21ec000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 264 bytes inside of
 2048-byte region [ffff8880a21ec000, ffff8880a21ec800)
The buggy address belongs to the page:
page:ffffea0002887b00 refcount:1 mapcount:0 mapping:ffff8880aa000e00 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002634248 ffffea000168a148 ffff8880aa000e00
raw: 0000000000000000 ffff8880a21ec000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a21ec000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a21ec080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a21ec100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8880a21ec180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a21ec200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================