syzbot


KASAN: use-after-free Read in fsnotify

Status: fixed on 2017/11/28 03:36
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+a7a0b7d4e88c6c7f5f6d6775f1938ba944d41bd8@syzkaller.appspotmail.com
Fix commit: b3a006600582 dnotify: Handle errors from fsnotify_add_mark_locked() in fcntl_dirnotify()
First crash: 2455d, last: 2455d

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in fsnotify+0x17c3/0x1af0 fs/notify/fsnotify.c:330
Read of size 8 at addr ffff8801d0407278 by task syz-executor4/5986

CPU: 0 PID: 5986 Comm: syz-executor4 Not tainted 4.14.0-rc2-mm1+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
RDS: rds_bind could not find a transport for 172.20.3.187, load rds_tcp or rds_rdma?
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 fsnotify+0x17c3/0x1af0 fs/notify/fsnotify.c:330
 fsnotify_close include/linux/fsnotify.h:241 [inline]
 __fput+0x221/0x7f0 fs/file_table.c:196
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x199/0x270 kernel/task_work.c:112
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0x9c8/0x1b00 kernel/exit.c:865
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73f/0x16d0 kernel/signal.c:2334
 do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:266 [inline]
 do_syscall_64+0x65c/0x8d0 arch/x86/entry/common.c:292
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x4520a9
RSP: 002b:00007f735732bc08 EFLAGS: 00000216 ORIG_RAX: 0000000000000029
RAX: 0000000000000025 RBX: 0000000000718000 RCX: 00000000004520a9
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 000000000000000a
RBP: 0000000000005990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004bb7b1
R13: 00000000ffffffff R14: 000000000000000a R15: 0000000000000006

Allocated by task 2963:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3561
 fsnotify_attach_connector_to_object fs/notify/mark.c:442 [inline]
 fsnotify_add_mark_list fs/notify/mark.c:523 [inline]
 fsnotify_add_mark_locked+0x3b5/0x10b0 fs/notify/mark.c:593
 inotify_new_watch fs/notify/inotify/inotify_user.c:567 [inline]
 inotify_update_watch fs/notify/inotify/inotify_user.c:594 [inline]
 SYSC_inotify_add_watch fs/notify/inotify/inotify_user.c:718 [inline]
 SyS_inotify_add_watch+0x6cd/0x820 fs/notify/inotify/inotify_user.c:668
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 93:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3503 [inline]
 kmem_cache_free+0x77/0x280 mm/slab.c:3763
 fsnotify_connector_destroy_workfn+0x82/0xa0 fs/notify/mark.c:170
 process_one_work+0xbfa/0x1bd0 kernel/workqueue.c:2119
 worker_thread+0x223/0x1860 kernel/workqueue.c:2253
 kthread+0x39c/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

The buggy address belongs to the object at ffff8801d0407258
 which belongs to the cache fsnotify_mark_connector of size 88
The buggy address is located 32 bytes inside of
 88-byte region [ffff8801d0407258, ffff8801d04072b0)
The buggy address belongs to the page:
page:ffffea00074101c0 count:1 mapcount:0 mapping:ffff8801d0407000 index:0xffff8801d0407078
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801d0407000 ffff8801d0407078 0000000100000020
raw: ffff8801d9887c40 ffff8801d9887c40 ffff8801d9884c80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d0407100: fb fb fb fb fb fb fb fb fb fc fc fc fc fb fb fb
 ffff8801d0407180: fb fb fb fb fb fb fb fb fc fc fc fc fb fb fb fb
>ffff8801d0407200: fb fb fb fb fb fb fb fc fc fc fc fb fb fb fb fb
                                                                ^
 ffff8801d0407280: fb fb fb fb fb fb fc fc fc fc 00 00 00 00 00 00
 ffff8801d0407300: 00 00 00 00 00 fc fc fc fc fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2017/09/28 11:41 mmots da2915ba6bbf c26ea367 .config console log report ci-upstream-mmots-kasan-gce
* Struck through repros no longer work on HEAD.