kernel BUG at security/keys/keyring.c:LINE!

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    befad944e231 Merge tag 'drm-fixes-2018-10-05' of git://ano..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=161fc976400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c0af03fe452b65fb
dashboard link: https://syzkaller.appspot.com/bug?extid=ec24e95ea483de0a24da
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10160e3a400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16995491400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ec24e95ea483de0a24da at syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at security/keys/keyring.c:1214!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 5807 Comm: syz-executor226 Not tainted 4.19.0-rc6+ #268
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__key_link_begin+0x23a/0x300 security/keys/keyring.c:1214
Code: fe 48 c7 c7 20 ae 67 89 e8 b3 36 23 fe eb ac e8 ec 64 42 fe 48 c7 c7  
20 ae 67 89 e8 30 73 73 04 e9 e3 fe ff ff e8 d6 64 42 fe <0f> 0b e8 cf 64  
42 fe 48 8d bb ce 00 00 00 48 b8 00 00 00 00 00 fc
RSP: 0018:ffff8801bbdc7b10 EFLAGS: 00010293
RAX: ffff8801d924e2c0 RBX: ffff8801d4e7e080 RCX: ffffffff833c4ebf
RDX: 0000000000000000 RSI: ffffffff833c50aa RDI: 0000000000000007
RBP: ffff8801bbdc7b40 R08: ffff8801d924e2c0 R09: fffffbfff12cf4a4
R10: fffffbfff12cf4a4 R11: ffffffff8967a523 R12: ffff8801bbdc7c48
R13: 0000000000000000 R14: ffff8801d4e7e200 R15: ffff8801d4e7e080
FS:  0000000001ce9880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020cab000 CR3: 00000001d829a000 CR4: 00000000001406f0
Call Trace:
  construct_alloc_key security/keys/request_key.c:389 [inline]
  construct_key_and_link security/keys/request_key.c:480 [inline]
  request_key_and_link+0x737/0x17a0 security/keys/request_key.c:593
  __do_sys_request_key security/keys/keyctl.c:213 [inline]
  __se_sys_request_key security/keys/keyctl.c:158 [inline]
  __x64_sys_request_key+0x305/0x400 security/keys/keyctl.c:158
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440169
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd70324808 EFLAGS: 00000217 ORIG_RAX: 00000000000000f9
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440169
RDX: 00000000200001c0 RSI: 0000000020000180 RDI: 00000000200000c0
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000111522d3 R11: 0000000000000217 R12: 00000000004019f0
R13: 0000000000401a80 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 40815c4a8f1e2472 ]---
RIP: 0010:__key_link_begin+0x23a/0x300 security/keys/keyring.c:1214
Code: fe 48 c7 c7 20 ae 67 89 e8 b3 36 23 fe eb ac e8 ec 64 42 fe 48 c7 c7  
20 ae 67 89 e8 30 73 73 04 e9 e3 fe ff ff e8 d6 64 42 fe <0f> 0b e8 cf 64  
42 fe 48 8d bb ce 00 00 00 48 b8 00 00 00 00 00 fc
RSP: 0018:ffff8801bbdc7b10 EFLAGS: 00010293
RAX: ffff8801d924e2c0 RBX: ffff8801d4e7e080 RCX: ffffffff833c4ebf
RDX: 0000000000000000 RSI: ffffffff833c50aa RDI: 0000000000000007
RBP: ffff8801bbdc7b40 R08: ffff8801d924e2c0 R09: fffffbfff12cf4a4
R10: fffffbfff12cf4a4 R11: ffffffff8967a523 R12: ffff8801bbdc7c48
R13: 0000000000000000 R14: ffff8801d4e7e200 R15: ffff8801d4e7e080
FS:  0000000001ce9880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020cab000 CR3: 00000001d829a000 CR4: 00000000001406f0


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller at googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches