linux-kernel - kernel BUG at fs/userfaultfd.c:LINE!

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Message-ID: <001a113a6870f5fed40560f49d0a@google.com>
Date:   Fri, 22 Dec 2017 13:37:01 -0800
From:   syzbot 
        <bot+83fec0ce1de1a860fbaa0774da1c839131b602a1@...kaller.appspotmail.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: kernel BUG at fs/userfaultfd.c:LINE!

Hello,

syzkaller hit the following crash on  
6084b576dca2e898f5c101baef151f7bfdbb606d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


------------[ cut here ]------------
kernel BUG at fs/userfaultfd.c:142!
invalid opcode: 0000 [#1] SMP
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3118 Comm: syzkaller879466 Not tainted  
4.15.0-rc3-next-20171214+ #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:userfaultfd_ctx_get+0x6d/0x70 fs/userfaultfd.c:142
RSP: 0000:ffffc900012f7c30 EFLAGS: 00010293
RAX: ffff8802134420c0 RBX: 0000000000000000 RCX: ffffffff8147a98d
RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffff880213659c40
RBP: ffffc900012f7c48 R08: 0000000000000000 R09: 0000000000000004
R10: ffffc900012f7cc0 R11: 0000000000000004 R12: ffff880213659c40
R13: ffff880214ed6000 R14: 0000000000000200 R15: 0000000000000000
FS:  00007fdf76164700(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020687000 CR3: 0000000211d48006 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  handle_userfault+0xd3/0xa00 fs/userfaultfd.c:445
  do_huge_pmd_anonymous_page+0x571/0x850 mm/huge_memory.c:707
  create_huge_pmd mm/memory.c:3838 [inline]
  __handle_mm_fault+0xc37/0x1930 mm/memory.c:4042
  handle_mm_fault+0x215/0x450 mm/memory.c:4108
  __do_page_fault+0x337/0x6b0 arch/x86/mm/fault.c:1429
  do_page_fault+0x52/0x330 arch/x86/mm/fault.c:1504
  page_fault+0x4c/0x60 arch/x86/entry/entry_64.S:1243
RIP: 0033:0x4453e5
RSP: 002b:0000000020687000 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000004453d9
RDX: 0000000020b4c000 RSI: 0000000020687000 RDI: 0000000000000600
RBP: 0000000000000000 R08: 00000000207a4f71 R09: 00007fdf76164700
R10: 0000000020552ffc R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffc6b2b2c2f R14: 00007fdf761649c0 R15: 0000000000000000
Code: 5b 41 5c 41 5d 5d c3 e8 d2 f9 e3 ff 85 db 74 16 e8 c9 f9 e3 ff 8d 53  
01 89 d8 f0 41 0f b1 55 00 89 c3 74 d7 eb e1 e8 b3 f9 e3 ff <0f> 0b 90 55  
48 89 e5 53 48 89 fb e8 a3 f9 e3 ff 48 83 3d 73 bb
RIP: userfaultfd_ctx_get+0x6d/0x70 fs/userfaultfd.c:142 RSP:  
ffffc900012f7c30
---[ end trace c25da3c687899c5a ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
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Please credit me with: Reported-by: syzbot <syzkaller@...glegroups.com>

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