Date:   Mon, 17 Dec 2018 21:31:02 -0800
From:   syzbot <syzbot+59722316960a71d9695b@...kaller.appspotmail.com>
To:     netdev@...r.kernel.org,
        syzkaller-upstream-moderation@...glegroups.com
Subject: KASAN: stack-out-of-bounds Read in apparmor_cred_prepare

Hello,

syzbot found the following crash on:

HEAD commit:    a28777f25031 ucc_geth: Add change_carrier() for Fixed PHYs
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16f3a885400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9655b05acfc97ff
dashboard link: https://syzkaller.appspot.com/bug?extid=59722316960a71d9695b
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
CC:             [jmorris@...ei.org john.johansen@...onical.com  
linux-kernel@...r.kernel.org linux-security-module@...r.kernel.org  
serge@...lyn.com]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+59722316960a71d9695b@...kaller.appspotmail.com

==================================================================
BUG: KASAN: stack-out-of-bounds in aa_get_newest_label  
security/apparmor/include/label.h:429 [inline]
BUG: KASAN: stack-out-of-bounds in apparmor_cred_prepare+0x562/0x5a0  
security/apparmor/lsm.c:80
kasan: CONFIG_KASAN_INLINE enabled
Read of size 8 at addr ffff8881da9c0c20 by task udevd/5686
kasan: GPF could be caused by NULL-ptr deref or user memory access

general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5686 Comm: udevd Not tainted 4.20.0-rc6+ #350
CPU: 0 PID: 5793 Comm: syz-executor3 Not tainted 4.20.0-rc6+ #350
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
Call Trace:
RIP: 0010:lookup_object lib/debugobjects.c:156 [inline]
RIP: 0010:debug_object_deactivate+0x191/0x450 lib/debugobjects.c:542
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x244/0x39d lib/dump_stack.c:113
------------[ cut here ]------------
Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected  
to SLAB object '.' (offset 18446744069414893726, size 2)!
WARNING: CPU: 0 PID: 5793 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_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  aa_get_newest_label security/apparmor/include/label.h:429 [inline]
  apparmor_cred_prepare+0x562/0x5a0 security/apparmor/lsm.c:80
  security_prepare_creds+0x60/0xc0 security/security.c:1022
  prepare_creds+0x3b9/0x4d0 kernel/cred.c:278
  do_coredump+0x52f/0x4001 fs/coredump.c:574
  get_signal+0x9ee/0x1980 kernel/signal.c:2511
  do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
  exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
  prepare_exit_to_usermode+0x342/0x3b0 arch/x86/entry/common.c:197
  retint_user+0x8/0x18
RIP: 0033:0x7fd2ffc90945
Code: 3b 10 f1 ff 1f c8 09 c9 da 81 88 ff ff 00 00 00 00 00 00 00 00 50 09  
c9 da 81 88 ff ff 04 f6 b1 86 ff ff ff ff e0 f5 b1 86 ff <ff> ff ff 01 00  
00 00 00 00 00 00 f0 09 c9 da 81 88 ff ff 63 db bf
RSP: 002b:00007ffd55eabe48 EFLAGS: 00010246
RAX: 0000000000000001 RBX: 00000000007c2110 RCX: 00007fd2ffc90943
RDX: 0000000000000004 RSI: 00007ffd55eabea0 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000001
R13: 00000000007d3a00 R14: 00000000007c2250 R15: 000000000000000b

The buggy address belongs to the object at ffff8881da9c0040
  which belongs to the cache @�ۢ���� of size -30591
The buggy address is located 33631 bytes to the right of
  -30591-byte region [ffff8881da9c0040, ffff8881da9b88c1)
The buggy address belongs to the page:
page:ffffea00076a7000 count:1 mapcount:0 mapping:ffff8881da800ac0 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea00076a4108 ffffea0007650a08 ffff8881da800ac0
raw: 0000000000000000 ffff8881da9c0040 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881da9c0b00: f1 00 f2 f2 f2 f2 f2 f2 f2 f8 f2 f2 f2 00 00 00
  ffff8881da9c0b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
> ffff8881da9c0c00: f1 f8 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00
                                ^
  ffff8881da9c0c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc 00
  ffff8881da9c0d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
==================================================================
Kernel Offset: disabled

======================================================
WARNING: possible circular locking dependency detected
4.20.0-rc6+ #350 Not tainted
------------------------------------------------------
syz-executor3/5793 is trying to acquire lock:
000000004475e30b ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70  
kernel/locking/semaphore.c:136

but task is already holding lock:
0000000033b07c4a (&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-executor3/5793:
  #0: 00000000ced00a2c (rcu_read_lock){....}, at: __skb_unlink  
include/linux/skbuff.h:1922 [inline]
  #0: 00000000ced00a2c (rcu_read_lock){....}, at: __skb_dequeue  
include/linux/skbuff.h:1938 [inline]
  #0: 00000000ced00a2c (rcu_read_lock){....}, at:  
process_backlog+0x1dd/0x7a0 net/core/dev.c:5921
  #1: 00000000ced00a2c (rcu_read_lock){....}, at: __skb_pull  
include/linux/skbuff.h:2155 [inline]
  #1: 00000000ced00a2c (rcu_read_lock){....}, at:  
ip_local_deliver_finish+0x13d/0x390 net/ipv4/ip_input.c:231
  #2: 000000006ec779e6 (hrtimer_bases.lock){-.-.}, at:  
hrtimer_interrupt+0xfc/0x780 kernel/time/hrtimer.c:1499
  #3: 0000000033b07c4a (&obj_hash[i].lock){-.-.}, at:  
debug_object_deactivate+0xf7/0x450 lib/debugobjects.c:540
  #4: 00000000ced00a2c (rcu_read_lock){....}, at:  
atomic_notifier_call_chain+0x0/0x190 kernel/notifier.c:329

stack backtrace:
CPU: 0 PID: 5793 Comm: syz-executor3 Not tainted 4.20.0-rc6+ #350
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
Rebooting in 86400 seconds..


---
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