mount_ns+0xc4/0x190 fs/super.c:1036
 proc_mount+0x7a/0x90 fs/proc/root.c:101
refcount_t: underflow; use-after-free.
 mount_fs+0x66/0x2d0 fs/super.c:1222
 vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037
WARNING: CPU: 0 PID: 4482 at lib/refcount.c:187 refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187
Kernel panic - not syncing: panic_on_warn set ...

 vfs_kern_mount fs/namespace.c:3292 [inline]
 kern_mount_data+0x50/0xb0 fs/namespace.c:3292
 pid_ns_prepare_proc+0x1e/0x80 fs/proc/root.c:222
 alloc_pid+0x87e/0xa00 kernel/pid.c:208
 copy_process.part.38+0x2516/0x4bd0 kernel/fork.c:1807
 copy_process kernel/fork.c:1606 [inline]
 _do_fork+0x1f7/0xf70 kernel/fork.c:2087
 SYSC_clone kernel/fork.c:2194 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2188
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x454e79
RSP: 002b:00007fac6a5c2c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fac6a5c36d4 RCX: 0000000000454e79
RDX: 00000000200008c0 RSI: 0000000020000800 RDI: 000000002000c100
RBP: 000000000072bea0 R08: 0000000020000940 R09: 0000000000000000
R10: 0000000020000900 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000051 R14: 00000000006f2838 R15: 0000000000000028
CPU: 0 PID: 4482 Comm: syz-executor7 Not tainted 4.16.0-rc7+ #373
proc_fill_super: allocate dentry failed
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
IPVS: ftp: loaded support on port[0] = 21
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x1f4/0x2b0 lib/bug.c:186
 fixup_bug.part.10+0x37/0x80 arch/x86/kernel/traps.c:178
 fixup_bug arch/x86/kernel/traps.c:247 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:986
RIP: 0010:refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187
RSP: 0018:ffff8801b9d9f318 EFLAGS: 00010282
RAX: dffffc0000000008 RBX: 0000000000000000 RCX: ffffffff815b193e
RDX: 0000000000000000 RSI: 1ffff100373b3e13 RDI: 1ffff100373b3de8
RBP: ffff8801b9d9f3a8 R08: 0000000000000000 R09: 0000000000000000
R10: ffff8801b9d9f2d0 R11: 0000000000000000 R12: 1ffff100373b3e64
R13: 00000000ffffffff R14: 0000000000000001 R15: ffff8801b3004720
 refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212
 kref_put include/linux/kref.h:69 [inline]
 put_pid_ns+0x9d/0xc0 kernel/pid_namespace.c:192
 free_nsproxy+0xfa/0x1f0 kernel/nsproxy.c:182
 switch_task_namespaces+0x9d/0xc0 kernel/nsproxy.c:229
 exit_task_namespaces+0x17/0x20 kernel/nsproxy.c:234
 copy_process.part.38+0x3aba/0x4bd0 kernel/fork.c:1988
 copy_process kernel/fork.c:1606 [inline]
 _do_fork+0x1f7/0xf70 kernel/fork.c:2087
 SYSC_clone kernel/fork.c:2194 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2188
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x454e79
RSP: 002b:00007fd1669b7c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fd1669b86d4 RCX: 0000000000454e79
RDX: 00000000200008c0 RSI: 0000000020000800 RDI: 000000002000c100
RBP: 000000000072bea0 R08: 0000000020000940 R09: 0000000000000000
R10: 0000000020000900 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000051 R14: 00000000006f2838 R15: 0000000000000028
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..