syzbot


KASAN: stack-out-of-bounds Read in __d_lookup

Status: auto-closed as invalid on 2019/06/13 16:28
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+26ced08d1e81ff6dd505@syzkaller.appspotmail.com
First crash: 1956d, last: 1929d

Sample crash report:
==================================================================
kasan: CONFIG_KASAN_INLINE enabled
BUG: KASAN: stack-out-of-bounds in __d_lookup+0x8bb/0x9e0 fs/dcache.c:2269
kasan: GPF could be caused by NULL-ptr deref or user memory access
Read of size 4 at addr ffff8881dae000e0 by task syz-executor4/6161
general protection fault: 0000 [#1] PREEMPT SMP KASAN

CPU: 0 PID: 7992 Comm: syz-executor3 Not tainted 4.20.0-rc6+ #345
CPU: 1 PID: 6161 Comm: syz-executor4 Not tainted 4.20.0-rc6+ #345
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:lookup_object lib/debugobjects.c:156 [inline]
RIP: 0010:debug_object_deactivate+0x191/0x450 lib/debugobjects.c:542
Call Trace:
------------[ cut here ]------------
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected to SLAB object '@' (offset 18446744069951467168, size 64)!
WARNING: CPU: 0 PID: 7992 at mm/usercopy.c:83 usercopy_warn+0xee/0x110 mm/usercopy.c:78
Kernel panic - not syncing: panic_on_warn set ...
 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 __d_lookup+0x8bb/0x9e0 fs/dcache.c:2269
 d_lookup+0x1e0/0x300 fs/dcache.c:2214
 mountpoint_last fs/namei.c:2657 [inline]
 path_mountpoint+0x1f1/0x2180 fs/namei.c:2695
 filename_mountpoint+0x245/0x460 fs/namei.c:2717
 user_path_mountpoint_at+0x37/0x40 fs/namei.c:2747
 ksys_umount+0x1c5/0x12d0 fs/namespace.c:1645
 __do_sys_umount fs/namespace.c:1671 [inline]
 __se_sys_umount fs/namespace.c:1669 [inline]
 __x64_sys_umount+0x54/0x80 fs/namespace.c:1669
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a0a7
Code: 44 00 00 b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 7d 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd17b777b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 00000000000241cd RCX: 000000000045a0a7
RDX: 000000000000000c RSI: 0000000000000002 RDI: 00007ffd17b788f0
RBP: 0000000000000127 R08: 0000000000000001 R09: 0000000002450940
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd17b788f0
R13: 0000000000024139 R14: 0000000000000000 R15: 0000000000000004

The buggy address belongs to the page:
page:ffffea00076b8000 count:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000001000(reserved)
raw: 02fffc0000001000 ffffea00076b8008 ffffea00076b8008 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881dadfff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881dae00000: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
>ffff8881dae00080: f1 00 f2 f2 f2 f2 f2 f2 f2 f8 f2 f2 f2 00 00 00
                                                       ^
 ffff8881dae00100: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
 ffff8881dae00180: f1 f8 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00
==================================================================
Kernel Offset: disabled

======================================================
WARNING: possible circular locking dependency detected
4.20.0-rc6+ #345 Not tainted
------------------------------------------------------
syz-executor3/7992 is trying to acquire lock:
00000000a09a80d5 ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
00000000f936b59e (&obj_hash[i].lock){-.-.}, at: debug_object_deactivate+0xf7/0x450 lib/debugobjects.c:540

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&obj_hash[i].lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
       __debug_object_init+0x127/0x1290 lib/debugobjects.c:383
       debug_object_init+0x16/0x20 lib/debugobjects.c:431
       debug_hrtimer_init kernel/time/hrtimer.c:410 [inline]
       debug_init kernel/time/hrtimer.c:458 [inline]
       hrtimer_init+0x97/0x490 kernel/time/hrtimer.c:1308
       init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1057
       __sched_fork+0x2ae/0x590 kernel/sched/core.c:2166
       init_idle+0x75/0x740 kernel/sched/core.c:5374
       sched_init+0xb33/0xc07 kernel/sched/core.c:6063
       start_kernel+0x4c1/0xa30 init/main.c:608
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #2 (&rq->lock){-.-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
       rq_lock kernel/sched/sched.h:1124 [inline]
       task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9802
       sched_fork+0x443/0xba0 kernel/sched/core.c:2359
       copy_process+0x25b8/0x87a0 kernel/fork.c:1887
       _do_fork+0x1cb/0x11d0 kernel/fork.c:2216
       kernel_thread+0x34/0x40 kernel/fork.c:2275
       rest_init+0x28/0x372 init/main.c:409
       arch_call_rest_init+0xe/0x1b
       start_kernel+0x9f5/0xa30 init/main.c:745
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #1 (&p->pi_lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
       try_to_wake_up+0xdc/0x1440 kernel/sched/core.c:1965
       wake_up_process+0x10/0x20 kernel/sched/core.c:2129
       __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
       up+0x13c/0x1c0 kernel/locking/semaphore.c:187
       __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236
       console_unlock+0x811/0x1190 kernel/printk/printk.c:2432
       vprintk_emit+0x391/0x990 kernel/printk/printk.c:1922
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
       vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
       printk+0xa7/0xcf kernel/printk/printk.c:1997
       check_stack_usage kernel/exit.c:755 [inline]
       do_exit.cold.18+0x57/0x16f kernel/exit.c:916
       do_group_exit+0x177/0x440 kernel/exit.c:970
       __do_sys_exit_group kernel/exit.c:981 [inline]
       __se_sys_exit_group kernel/exit.c:979 [inline]
       __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:979
       do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 ((console_sem).lock){-.-.}:

other info that might help us debug this:

Chain exists of:
  (console_sem).lock --> &rq->lock --> &obj_hash[i].lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&obj_hash[i].lock);
                               lock(&rq->lock);
                               lock(&obj_hash[i].lock);
  lock((console_sem).lock);

 *** DEADLOCK ***

5 locks held by syz-executor3/7992:
 #0: 000000001bfd9888 (rcu_read_lock){....}, at: __skb_unlink include/linux/skbuff.h:1922 [inline]
 #0: 000000001bfd9888 (rcu_read_lock){....}, at: __skb_dequeue include/linux/skbuff.h:1938 [inline]
 #0: 000000001bfd9888 (rcu_read_lock){....}, at: process_backlog+0x1dd/0x7a0 net/core/dev.c:5910
 #1: 000000001bfd9888 (rcu_read_lock){....}, at: __skb_pull include/linux/skbuff.h:2155 [inline]
 #1: 000000001bfd9888 (rcu_read_lock){....}, at: ip_local_deliver_finish+0x13d/0x390 net/ipv4/ip_input.c:231
 #2: 00000000f4ec76ed (hrtimer_bases.lock){-.-.}, at: hrtimer_interrupt+0xfc/0x780 kernel/time/hrtimer.c:1499
 #3: 00000000f936b59e (&obj_hash[i].lock){-.-.}, at: debug_object_deactivate+0xf7/0x450 lib/debugobjects.c:540
 #4: 000000001bfd9888 (rcu_read_lock){....}, at: atomic_notifier_call_chain+0x0/0x190 kernel/notifier.c:329

stack backtrace:
CPU: 0 PID: 7992 Comm: syz-executor3 Not tainted 4.20.0-rc6+ #345
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
Rebooting in 86400 seconds..

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/12/15 16:28 net-next-old b9948e111391 c9128939 .config console log report ci-upstream-net-kasan-gce
2018/11/27 19:21 net-next-old 02c72d5edadc 4b6d14f2 .config console log report ci-upstream-net-kasan-gce
2018/11/19 05:41 net-next-old cddaf02bcb73 adf636a8 .config console log report ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.