general protection fault in kstrtouint

[syzbot <syzbot+657c927f261cbdd5c50f@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    2b769bb85b48 Add linux-next specific files for 20180807
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1525beac400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=547d800b8773c2c5
dashboard link: https://syzkaller.appspot.com/bug?extid=657c927f261cbdd5c50f
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=170cdffc400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=160f7830400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+657c927f261cbdd5c50f@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 0 PID: 4328 Comm: syz-executor623 Not tainted  
4.18.0-rc8-next-20180807+ #33
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:kstrtoull lib/kstrtox.c:123 [inline]
RIP: 0010:kstrtouint+0x83/0x1b0 lib/kstrtox.c:222
Code: f1 f1 c7 40 04 00 f2 f2 f2 65 48 8b 04 25 28 00 00 00 48 89 45 d0 31  
c0 e8 1a 31 18 fe 48 89 d8 48 89 da 48 c1 e8 03 83 e2 07 <42> 0f b6 04 30  
38 d0 7f 08 84 c0 0f 85 e8 00 00 00 44 0f b6 33 bf
RSP: 0018:ffff8801ad63f888 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff10035ac7f5f
RDX: 0000000000000000 RSI: ffffffff8364fc96 RDI: 0000000000000000
RBP: ffff8801ad63f918 R08: ffff8801ad5da3c0 R09: ffff8801ad588580
R10: 00000000900ed4cc R11: ffff8801db0236b3 R12: 1ffff10035ac7f12
R13: ffff8801ad63fa18 R14: dffffc0000000000 R15: ffff8801ad63f8f0
FS:  0000000001d3b880(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbd50b94518 CR3: 00000001c46c3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  fs_parse+0xb8d/0x1130 fs/fs_parser.c:164
  hugetlbfs_parse_param+0xd1/0xa50 fs/hugetlbfs/inode.c:1210
  vfs_parse_fs_param+0x196/0x2c0 fs/fs_context.c:162
  vfs_parse_fs_string+0x1d5/0x2b0 fs/fs_context.c:191
  generic_parse_monolithic+0x17c/0x210 fs/fs_context.c:228
  parse_monolithic_mount_data fs/namespace.c:2320 [inline]
  do_new_mount fs/namespace.c:2599 [inline]
  do_mount+0x6d8/0x1e30 fs/namespace.c:2927
  ksys_mount+0x12d/0x140 fs/namespace.c:3143
  __do_sys_mount fs/namespace.c:3157 [inline]
  __se_sys_mount fs/namespace.c:3154 [inline]
  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3154
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4441a9
Code: 0d d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 db d7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcb4f5f8a8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00000000004441a9
RDX: 0000000020000300 RSI: 0000000020000340 RDI: 0000000020000000
RBP: 00000000006cf018 R08: 00000000200001c0 R09: 00000000200001c0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000401e10
R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
Dumping ftrace buffer:
    (ftrace buffer empty)
---[ end trace 3277e6ee2f78e7e4 ]---
RIP: 0010:kstrtoull lib/kstrtox.c:123 [inline]
RIP: 0010:kstrtouint+0x83/0x1b0 lib/kstrtox.c:222
Code: f1 f1 c7 40 04 00 f2 f2 f2 65 48 8b 04 25 28 00 00 00 48 89 45 d0 31  
c0 e8 1a 31 18 fe 48 89 d8 48 89 da 48 c1 e8 03 83 e2 07 <42> 0f b6 04 30  
38 d0 7f 08 84 c0 0f 85 e8 00 00 00 44 0f b6 33 bf
RSP: 0018:ffff8801ad63f888 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff10035ac7f5f
RDX: 0000000000000000 RSI: ffffffff8364fc96 RDI: 0000000000000000
RBP: ffff8801ad63f918 R08: ffff8801ad5da3c0 R09: ffff8801ad588580
R10: 00000000900ed4cc R11: ffff8801db0236b3 R12: 1ffff10035ac7f12
R13: ffff8801ad63fa18 R14: dffffc0000000000 R15: ffff8801ad63f8f0
FS:  0000000001d3b880(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbd50b94518 CR3: 00000001c46c3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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