KASAN: use-after-free Write in fsnotify_detach_connector_from_object

Status: fixed on 2020/07/17 17:58
Subsystems: fs
[Documentation on labels]
Fix commit: ef1548adada5 proc: Use new_inode not new_inode_pseudo
First crash: 1468d, last: 1459d
Cause bisection: introduced by (bisect log) :
commit 76313c70c52f930af4afd21684509ca52297ea71
Author: Eric W. Biederman <>
Date: Wed Feb 19 16:37:15 2020 +0000

  uml: Create a private mount of proc for mconsole

Crash: general protection fault in batadv_iv_ogm_schedule_buff (log)
Repro: C syz .config
Discussions (10)
Title Replies (including bot) Last reply
[PATCH 4.9 000/128] 4.9.228-rc1 review 135 (135) 2021/02/26 19:09
[PATCH 5.4 000/134] 5.4.47-rc1 review 141 (141) 2021/01/28 17:06
[PATCH 4.19 000/267] 4.19.129-rc1 review 280 (280) 2020/06/30 01:36
[PATCH 4.14 000/190] 4.14.185-rc1 review 197 (197) 2020/06/26 07:05
[PATCH 4.4 000/101] 4.4.228-rc1 review 109 (109) 2020/06/20 15:06
[PATCH 5.6 000/161] 5.6.19-rc1 review 164 (164) 2020/06/16 17:11
[PATCH 5.7 000/163] 5.7.3-rc1 review 164 (164) 2020/06/16 15:35
[PATCH] proc: Use new_inode not new_inode_pseudo 2 (2) 2020/06/15 07:38
[GIT PULL] proc changes for v5.8-rc1 10 (10) 2020/06/12 22:47
KASAN: use-after-free Write in fsnotify_detach_connector_from_object 0 (1) 2020/06/12 09:24

Sample crash report:
BUG: KASAN: use-after-free in atomic64_inc include/asm-generic/atomic-instrumented.h:1049 [inline]
BUG: KASAN: use-after-free in atomic_long_inc include/asm-generic/atomic-long.h:160 [inline]
BUG: KASAN: use-after-free in fsnotify_detach_connector_from_object+0x25e/0x380 fs/notify/mark.c:185
Write of size 8 at addr ffff8880950a07c0 by task syz-executor196/6838

CPU: 1 PID: 6838 Comm: syz-executor196 Not tainted 5.7.0-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+0xd3/0x413 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x141/0x190 mm/kasan/generic.c:192
 atomic64_inc include/asm-generic/atomic-instrumented.h:1049 [inline]
 atomic_long_inc include/asm-generic/atomic-long.h:160 [inline]
 fsnotify_detach_connector_from_object+0x25e/0x380 fs/notify/mark.c:185
 fsnotify_put_mark+0x367/0x580 fs/notify/mark.c:250
 fsnotify_clear_marks_by_group+0x33f/0x490 fs/notify/mark.c:764
 fsnotify_destroy_group+0xc9/0x300 fs/notify/group.c:61
 inotify_release+0x33/0x40 fs/notify/inotify/inotify_user.c:271
 __fput+0x33e/0x880 fs/file_table.c:281
 task_work_run+0xf4/0x1b0 kernel/task_work.c:123
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xb3f/0x2de0 kernel/exit.c:806
 do_group_exit+0x125/0x340 kernel/exit.c:904
 __do_sys_exit_group kernel/exit.c:915 [inline]
 __se_sys_exit_group kernel/exit.c:913 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:913
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
RIP: 0033:0x445368
Code: 00 00 be 3c 00 00 00 eb 19 66 0f 1f 84 00 00 00 00 00 48 89 d7 89 f0 0f 05 48 3d 00 f0 ff ff 77 21 f4 48 89 d7 44 89 c0 0f 05 <48> 3d 00 f0 ff ff 76 e0 f7 d8 64 41 89 01 eb d8 0f 1f 84 00 00 00
RSP: 002b:00007ffd395ea5a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445368
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004cc9f0 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 000000037ffffa00 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006e0320 R14: 000000000000002d R15: 20c49ba5e353f7cf

Allocated by task 6839:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc mm/kasan/common.c:494 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467
 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 alloc_super+0x52/0x9d0 fs/super.c:203
 sget_fc+0x13f/0x790 fs/super.c:530
 vfs_get_super+0x6d/0x2d0 fs/super.c:1186
 vfs_get_tree+0x89/0x2f0 fs/super.c:1547
 do_new_mount fs/namespace.c:2874 [inline]
 do_mount+0x1306/0x1b40 fs/namespace.c:3199
 __do_sys_mount fs/namespace.c:3409 [inline]
 __se_sys_mount fs/namespace.c:3386 [inline]
 __x64_sys_mount+0x18f/0x230 fs/namespace.c:3386
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295

Freed by task 2475:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351

The buggy address belongs to the object at ffff8880950a0000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1984 bytes inside of
 4096-byte region [ffff8880950a0000, ffff8880950a1000)
The buggy address belongs to the page:
page:ffffea0002542800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea0002542800 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00023b6e88 ffffea00027e3e08 ffff8880aa002000
raw: 0000000000000000 ffff8880950a0000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880950a0680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880950a0700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880950a0780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880950a0800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880950a0880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/06/08 10:56 upstream 7ae77150d94d 7751efd0 .config console log report syz C ci-upstream-kasan-gce-selinux-root
2020/06/08 09:50 upstream 7ae77150d94d 7751efd0 .config console log report syz C ci-upstream-kasan-gce
2020/06/16 21:09 upstream 7ae77150d94d 559fbe2d .config console log report ci-upstream-kasan-gce
2020/06/08 09:19 upstream 7ae77150d94d 7751efd0 .config console log report ci-upstream-kasan-gce
* Struck through repros no longer work on HEAD.