kernel panic: MAC Initialization failed. (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7b827ff9af88 Add linux-next specific files for 20190227
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10f71894c00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5fa6b8975759dcc5
dashboard link: https://syzkaller.appspot.com/bug?extid=29569ed06425fcf67a95
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=113a8242c00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=154d6bd0c00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+29569e...@syzkaller.appspotmail.com

Code: e8 0c ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 bb 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffca1453958 EFLAGS: 00000246 ORIG_RAX: 000000000000003b
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000440ff9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 00007ffca1453970 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000
ERROR: Out of memory at tomoyo_realpath_from_path.
Kernel panic - not syncing: MAC Initialization failed.
CPU: 0 PID: 7505 Comm: syz-executor695 Not tainted 5.0.0-rc8-next-20190227
#44
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+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2cb/0x65c kernel/panic.c:214
tomoyo_warn_oom.cold+0x35/0x43 security/tomoyo/memory.c:28
tomoyo_realpath_from_path+0x3a8/0x730 security/tomoyo/realpath.c:320
tomoyo_realpath_nofollow+0xc8/0xdb security/tomoyo/realpath.c:336
tomoyo_find_next_domain+0x28c/0x1f8a security/tomoyo/domain.c:725
tomoyo_bprm_check_security security/tomoyo/tomoyo.c:107 [inline]
tomoyo_bprm_check_security+0x12a/0x1b0 security/tomoyo/tomoyo.c:97
security_bprm_check+0x69/0xb0 security/security.c:751
search_binary_handler+0x77/0x570 fs/exec.c:1644
exec_binprm fs/exec.c:1698 [inline]
__do_execve_file.isra.0+0x1394/0x23f0 fs/exec.c:1818
do_execveat_common fs/exec.c:1865 [inline]
do_execve fs/exec.c:1882 [inline]
__do_sys_execve fs/exec.c:1958 [inline]
__se_sys_execve fs/exec.c:1953 [inline]
__x64_sys_execve+0x8f/0xc0 fs/exec.c:1953
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440ff9
Code: e8 0c ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 bb 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffca1453958 EFLAGS: 00000246 ORIG_RAX: 000000000000003b
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000440ff9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 00007ffca1453970 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[Tetsuo Handa]

On 2019/02/28 15:42, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    7b827ff9af88 Add linux-next specific files for 20190227
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10f71894c00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5fa6b8975759dcc5
> dashboard link: https://syzkaller.appspot.com/bug?extid=29569ed06425fcf67a95
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=113a8242c00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154d6bd0c00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+29569e...@syzkaller.appspotmail.com
>

Memory allocation failure due to fault injection before loading policy.

#syz dup: kernel panic: MAC Initialization failed.

[Dmitry Vyukov]

How/why is not this "user crashes system"? Kernel must not panic on
OOM. There is memcg as well.