general protection fault in mqueue_get_tree

general protection fault in mqueue_get_tree

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    7c1b097f27bf Add linux-next specific files for 20180912
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1667ea56400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5980033172920ec0
dashboard link: https://syzkaller.appspot.com/bug?extid=885a82aa44fba12672b3
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12129aae400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11473121400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+885a82aa44fba12672b3@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] PREEMPT SMP KASAN
CPU: 1 PID: 5559 Comm: syz-executor976 Not tainted  
4.19.0-rc3-next-20180912+ #72
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:mqueue_get_tree+0xba/0x2e0 ipc/mqueue.c:362
Code: 4c 8d b3 98 00 00 00 4d 85 ed 0f 84 d1 00 00 00 e8 6b 44 3f fe 49 8d  
7d 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 e3 01 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b
RSP: 0018:ffff8801bbaf7928 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff8801cc909b40 RCX: ffffffff8160aca1
RDX: 0000000000018006 RSI: ffffffff833deb15 RDI: 00000000000c0032
RBP: ffff8801bbaf7948 R08: fffffbfff13555fd R09: fffffbfff13555fc
R10: fffffbfff13555fc R11: ffffffff89aaafe3 R12: ffff8801d7ac00c0
R13: 00000000000c002a R14: ffff8801cc909bd8 R15: ffff8801cc909bd8
FS:  0000000001816880(0000) GS:ffff8801dad00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004776a0 CR3: 00000001d8e4b000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  vfs_get_tree+0x1cb/0x5c0 fs/super.c:1787
  mq_create_mount+0xe3/0x190 ipc/mqueue.c:415
  mq_init_ns+0x15a/0x210 ipc/mqueue.c:1621
  create_ipc_ns ipc/namespace.c:58 [inline]
  copy_ipcs+0x3d2/0x580 ipc/namespace.c:84
  create_new_namespaces+0x376/0x900 kernel/nsproxy.c:87
  unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:206
  ksys_unshare+0x79c/0x10b0 kernel/fork.c:2535
  __do_sys_unshare kernel/fork.c:2603 [inline]
  __se_sys_unshare kernel/fork.c:2601 [inline]
  __x64_sys_unshare+0x31/0x40 kernel/fork.c:2601
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44e717
Code: 00 00 00 b8 63 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 bd 9a fb ff c3  
66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 10 01 00 00 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 9d 9a fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdc5a0a4e8 EFLAGS: 00000217 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007ffdc5a0a660 RCX: 000000000044e717
RDX: 0000000000000000 RSI: 00007ffdc5a0a500 RDI: 0000000008000000
RBP: 585858582e72656c R08: 0000000000000000 R09: 0000000000000018
R10: 0000000000000000 R11: 0000000000000217 R12: 6c616b7a79732f2e
R13: 00000000004086d0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 45e54bf7dc140f15 ]---
RIP: 0010:mqueue_get_tree+0xba/0x2e0 ipc/mqueue.c:362
Code: 4c 8d b3 98 00 00 00 4d 85 ed 0f 84 d1 00 00 00 e8 6b 44 3f fe 49 8d  
7d 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 e3 01 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b
RSP: 0018:ffff8801bbaf7928 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff8801cc909b40 RCX: ffffffff8160aca1
RDX: 0000000000018006 RSI: ffffffff833deb15 RDI: 00000000000c0032
RBP: ffff8801bbaf7948 R08: fffffbfff13555fd R09: fffffbfff13555fc
R10: fffffbfff13555fc R11: ffffffff89aaafe3 R12: ffff8801d7ac00c0
R13: 00000000000c002a R14: ffff8801cc909bd8 R15: ffff8801cc909bd8
FS:  0000000001816880(0000) GS:ffff8801dad00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004776a0 CR3: 00000001d8e4b000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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