KASAN: use-after-free Read in tty_open

Status: fixed on 2020/05/10 10:41
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+9af6d43c1beabec8fd05@syzkaller.appspotmail.com
Fix commit: ca4463bf8438 vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console
First crash: 2448d, last: 2336d
Cause bisection: introduced by (bisect log) :
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31
Author: Russell Currey <ruscur@russell.cc>
Date: Mon Feb 8 04:08:20 2016 +0000

  powerpc/powernv: Remove support for p5ioc2

Crash: BUG: spinlock lockup suspected in nf_conntrack_lock (log)
Repro: C syz .config
  
Fix bisection: fixed by (bisect log) :
commit ca4463bf8438b403596edd0ec961ca0d4fbe0220
Author: Eric Biggers <ebiggers@google.com>
Date: Sun Mar 22 03:43:04 2020 +0000

  vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console

  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in tty_open 2 (5) 2020/04/25 02:18
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: use-after-free Read in tty_open 19 syz, C done 5 2347d 2449d 1/1 fixed on 2020/04/13 10:52
android-5-15 KASAN: use-after-free Read in tty_open origin:upstream 19 syz 1 4d05h 4d05h 0/2 premoderation: reported syz repro on 2026/08/13 02:17
linux-4.19 KASAN: use-after-free Read in tty_open 19 syz, C done 2 2343d 2449d 1/1 fixed on 2020/04/17 06:51
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2020/04/24 20:21 4h01m bisect fix upstream OK (1) job log
2020/03/15 00:56 21m bisect fix upstream OK (0) job log log
2020/01/26 22:04 21m bisect fix upstream OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in test_bit include/asm-generic/bitops/instrumented-non-atomic.h:110 [inline]
BUG: KASAN: use-after-free in tty_port_kopened include/linux/tty.h:673 [inline]
BUG: KASAN: use-after-free in tty_open_by_driver drivers/tty/tty_io.c:1966 [inline]
BUG: KASAN: use-after-free in tty_open+0x6f8/0xbb0 drivers/tty/tty_io.c:2035
Read of size 8 at addr ffff888094827200 by task syz-executor028/7270

CPU: 1 PID: 7270 Comm: syz-executor028 Not tainted 5.5.0-rc1-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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:639
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
 __kasan_check_read+0x11/0x20 mm/kasan/common.c:95
 test_bit include/asm-generic/bitops/instrumented-non-atomic.h:110 [inline]
 tty_port_kopened include/linux/tty.h:673 [inline]
 tty_open_by_driver drivers/tty/tty_io.c:1966 [inline]
 tty_open+0x6f8/0xbb0 drivers/tty/tty_io.c:2035
 chrdev_open+0x245/0x6b0 fs/char_dev.c:414
 do_dentry_open+0x4e6/0x1380 fs/open.c:797
 vfs_open+0xa0/0xd0 fs/open.c:914
 do_last fs/namei.c:3420 [inline]
 path_openat+0x10df/0x4500 fs/namei.c:3537
 do_filp_open+0x1a1/0x280 fs/namei.c:3567
 do_sys_open+0x3fe/0x5d0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1110
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x405bc1
Code: 75 14 b8 02 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 a4 18 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 02 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:00007f4c82a59830 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00000000006dcc28 RCX: 0000000000405bc1
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00007f4c82a59860
RBP: 00000000006dcc20 R08: 0000000000000000 R09: 000000000000000d
R10: 0000000000000064 R11: 0000000000000293 R12: 00000000006dcc2c
R13: 00007ffd46915f6f R14: 00007f4c82a5a9c0 R15: 0000000000000000

Allocated by task 9185:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527
 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:670 [inline]
 vc_allocate drivers/tty/vt/vt.c:1085 [inline]
 vc_allocate+0x1fc/0x760 drivers/tty/vt/vt.c:1066
 con_install+0x52/0x410 drivers/tty/vt/vt.c:3229
 tty_driver_install_tty drivers/tty/tty_io.c:1228 [inline]
 tty_init_dev drivers/tty/tty_io.c:1341 [inline]
 tty_init_dev+0xf9/0x470 drivers/tty/tty_io.c:1318
 tty_open_by_driver drivers/tty/tty_io.c:1987 [inline]
 tty_open+0x4a5/0xbb0 drivers/tty/tty_io.c:2035
 chrdev_open+0x245/0x6b0 fs/char_dev.c:414
 do_dentry_open+0x4e6/0x1380 fs/open.c:797
 vfs_open+0xa0/0xd0 fs/open.c:914
 do_last fs/namei.c:3420 [inline]
 path_openat+0x10df/0x4500 fs/namei.c:3537
 do_filp_open+0x1a1/0x280 fs/namei.c:3567
 do_sys_open+0x3fe/0x5d0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1110
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7272:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:335 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:474
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 vt_disallocate_all+0x2bd/0x3e0 drivers/tty/vt/vt_ioctl.c:323
 vt_ioctl+0xc38/0x26d0 drivers/tty/vt/vt_ioctl.c:816
 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888094827000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 512 bytes inside of
 2048-byte region [ffff888094827000, ffff888094827800)
The buggy address belongs to the page:
page:ffffea00025209c0 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0
raw: 00fffe0000000200 ffffea00028ea288 ffffea00028a5208 ffff8880aa400e00
raw: 0000000000000000 ffff888094827000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888094827100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888094827180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888094827200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888094827280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888094827300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/12/15 09:11 upstream 07c4b9e9f71a eef6e580 .config console log report syz C ci-upstream-kasan-gce-root
2019/12/14 15:43 upstream e31736d9fae8 eef6e580 .config console log report syz C ci-upstream-kasan-gce-selinux-root
2019/12/04 04:17 upstream 76bb8b05960c ae13a849 .config console log report syz C ci-upstream-kasan-gce-root
2019/12/03 22:19 upstream 76bb8b05960c ae13a849 .config console log report syz C ci-upstream-kasan-gce-root
2019/12/03 21:20 upstream 76bb8b05960c ae13a849 .config console log report syz C ci-upstream-kasan-gce-selinux-root
2019/12/04 00:07 upstream 76bb8b05960c ae13a849 .config console log report syz C ci-upstream-kasan-gce-386
2019/12/26 04:47 linux-next 7ddd09fc4b74 be5c2c81 .config console log report syz C ci-upstream-linux-next-kasan-gce-root
2020/03/24 22:22 linux-next 770fbb32d34e 68660b21 .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.