linux-next boot error: general protection fault in do_mount_root

[syzbot <syzbot+31f37c1dc3fd9e900602@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    cf2be78b Add linux-next specific files for 20191216
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13f505dee00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=634b7ce01f79423d
dashboard link: https://syzkaller.appspot.com/bug?extid=31f37c1dc3fd9e900602
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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+31f37c1dc3fd9e900602@syzkaller.appspotmail.com

batman_adv: B.A.T.M.A.N. advanced 2019.5 (compatibility version 15) loaded
openvswitch: Open vSwitch switching datapath
NET: Registered protocol family 40
mpls_gso: MPLS GSO support
IPI shorthand broadcast: enabled
AVX2 version of gcm_enc/dec engaged.
AES CTR mode by8 optimization enabled
sched_clock: Marking stable (12282186706, 24150593)->(12316857222,  
-10519923)
registered taskstats version 1
Loading compiled-in X.509 certificates
Loaded X.509 cert 'Build time autogenerated kernel key:  
8b22f477d966bfa6cf9a482acbda6ca1892a4acc'
zswap: loaded using pool lzo/zbud
Key type ._fscrypt registered
Key type .fscrypt registered
Btrfs loaded, crc32c=crc32c-intel
Key type big_key registered
Key type encrypted registered
AppArmor: AppArmor sha1 policy hashing enabled
ima: No TPM chip found, activating TPM-bypass!
ima: Allocated hash algorithm: sha256
ima: No architecture policies found
evm: Initialising EVM extended attributes:
evm: security.selinux
evm: security.SMACK64
evm: security.SMACK64EXEC
evm: security.SMACK64TRANSMUTE
evm: security.SMACK64MMAP
evm: security.apparmor
evm: security.ima
evm: security.capability
evm: HMAC attrs: 0x1
PM:   Magic number: 15:311:439
media media3: hash matches
printk: console [netcon0] enabled
netconsole: network logging started
gtp: GTP module loaded (pdp ctx size 104 bytes)
rdma_rxe: loaded
cfg80211: Loading compiled-in X.509 certificates for regulatory database
cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
ALSA device list:
   #0: Dummy 1
   #1: Loopback 1
   #2: Virtual MIDI Card 1
md: Waiting for all devices to be available before autodetect
md: If you don't use raid, use raid=noautodetect
md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.5.0-rc2-next-20191216-syzkaller  
#0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:strncpy+0x35/0xc0 lib/string.c:119
Code: e5 41 56 41 55 4c 8d 34 17 49 bd 00 00 00 00 00 fc ff df 41 54 53 48  
89 fb 48 83 ec 10 48 89 f2 48 89 f1 48 c1 ea 03 83 e1 07 <42> 0f b6 14 2a  
38 ca 7f 04 84 d2 75 40 48 89 da 48 89 d9 44 0f b6
RSP: 0000:ffffc90000c7fca8 EFLAGS: 00010246
RAX: ffff888099090000 RBX: ffff888099090000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888099090000
RBP: ffffc90000c7fcd8 R08: ffff888099090000 R09: ffffed1015d07074
R10: ffffed1015d07073 R11: ffff8880ae83839b R12: ffffea0002642400
R13: dffffc0000000000 R14: ffff888099090fff R15: ffff888214cc3000
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000986d000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  strncpy include/linux/string.h:326 [inline]
  do_mount_root+0x74/0x23b init/do_mounts.c:404
  mount_block_root+0x342/0x51a init/do_mounts.c:438
  mount_root+0x283/0x2cd init/do_mounts.c:628
  prepare_namespace+0x26f/0x2a7 init/do_mounts.c:687
  kernel_init_freeable+0x557/0x570 init/main.c:1233
  kernel_init+0x12/0x1bf init/main.c:1112
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace c645a4d31f27fe8a ]---
RIP: 0010:strncpy+0x35/0xc0 lib/string.c:119
Code: e5 41 56 41 55 4c 8d 34 17 49 bd 00 00 00 00 00 fc ff df 41 54 53 48  
89 fb 48 83 ec 10 48 89 f2 48 89 f1 48 c1 ea 03 83 e1 07 <42> 0f b6 14 2a  
38 ca 7f 04 84 d2 75 40 48 89 da 48 89 d9 44 0f b6
RSP: 0000:ffffc90000c7fca8 EFLAGS: 00010246
RAX: ffff888099090000 RBX: ffff888099090000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888099090000
RBP: ffffc90000c7fcd8 R08: ffff888099090000 R09: ffffed1015d07074
R10: ffffed1015d07073 R11: ffff8880ae83839b R12: ffffea0002642400
R13: dffffc0000000000 R14: ffff888099090fff R15: ffff888214cc3000
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000986d000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.