syzbot

audit: type=1400 audit(1585471473.165:36): avc:  denied  { map } for  pid=7442 comm="syz-executor729" path="/root/syz-executor729721826" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in con_shutdown+0x7f/0x90 drivers/tty/vt/vt.c:2928
Write of size 8 at addr ffff888093e03748 by task syz-executor729/7450

CPU: 1 PID: 7450 Comm: syz-executor729 Not tainted 4.14.174-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:2928
 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
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x9f2/0x2b00 kernel/exit.c:858
 do_group_exit+0x100/0x310 kernel/exit.c:955
 SYSC_exit_group kernel/exit.c:966 [inline]
 SyS_exit_group+0x19/0x20 kernel/exit.c:964
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43ff38
RSP: 002b:00007ffc6b69a188 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ff38
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004bf950 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d2180 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7450:
 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:2879
 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:888
 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:1081
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 7451:
 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 ffff888093e03640
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 264 bytes inside of
 2048-byte region [ffff888093e03640, ffff888093e03e40)
The buggy address belongs to the page:
page:ffffea00024f8080 count:1 mapcount:0 mapping:ffff888093e02540 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff888093e02540 0000000000000000 0000000100000003
raw: ffffea00024b44a0 ffffea00024f1a20 ffff88812fe56c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888093e03600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff888093e03680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888093e03700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888093e03780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888093e03800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================