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BUG: KASAN: use-after-free in con_shutdown+0x7f/0x90 drivers/tty/vt/vt.c:3287
Write of size 8 at addr ffff88809ef89108 by task syz-executor689/9557

CPU: 1 PID: 9557 Comm: syz-executor689 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
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xb34/0x2dd0 kernel/exit.c:801
 do_group_exit+0x125/0x340 kernel/exit.c:899
 __do_sys_exit_group kernel/exit.c:910 [inline]
 __se_sys_exit_group kernel/exit.c:908 [inline]
 __ia32_sys_exit_group+0x3a/0x50 kernel/exit.c:908
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x270/0xe8f arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Allocated by task 9557:
 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:1146
 do_sys_open+0xc3/0x140 fs/open.c:1162
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x270/0xe8f arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 9556:
 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
 vt_compat_ioctl+0x410/0x710 drivers/tty/vt/vt_ioctl.c:1237
 tty_compat_ioctl+0x19c/0x410 drivers/tty/tty_io.c:2849
 __do_compat_sys_ioctl fs/ioctl.c:857 [inline]
 __se_compat_sys_ioctl fs/ioctl.c:808 [inline]
 __ia32_compat_sys_ioctl+0x23d/0x2b0 fs/ioctl.c:808
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x270/0xe8f arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

The buggy address belongs to the object at ffff88809ef89000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 264 bytes inside of
 2048-byte region [ffff88809ef89000, ffff88809ef89800)
The buggy address belongs to the page:
page:ffffea00027be240 refcount:1 mapcount:0 mapping:ffff8880aa000e00 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029f7b08 ffffea0002a2a988 ffff8880aa000e00
raw: 0000000000000000 ffff88809ef89000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809ef89000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809ef89080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809ef89100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88809ef89180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809ef89200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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