net: warning in inet_sock_destruct

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit c470abd4fde40ea6a0846a2beab642a578c0b8cd (4.10).

A reproducer and .config are attached.

------------[ cut here ]------------
WARNING: CPU: 2 PID: 4776 at net/ipv4/af_inet.c:152
inet_sock_destruct+0x7c7/0x9d0 net/ipv4/af_inet.c:152
Kernel panic - not syncing: panic_on_warn set ...

CPU: 2 PID: 4776 Comm: syz-executor0 Not tainted 4.10.0-rc8+ #201
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:15 [inline]
 dump_stack+0x292/0x398 lib/dump_stack.c:51
 panic+0x1cb/0x3a9 kernel/panic.c:179
 __warn+0x1c4/0x1e0 kernel/panic.c:539
 warn_slowpath_null+0x2c/0x40 kernel/panic.c:582
 inet_sock_destruct+0x7c7/0x9d0 net/ipv4/af_inet.c:152
 __sk_destruct+0xe1/0x6e0 net/core/sock.c:1430
 __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 rcu_do_batch.isra.67+0x900/0xc50 kernel/rcu/tree.c:2780
 invoke_rcu_callbacks kernel/rcu/tree.c:3043 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:3010 [inline]
 rcu_process_callbacks+0x2b7/0xba0 kernel/rcu/tree.c:3027
 __do_softirq+0x2fb/0xb7d kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x19e/0x1d0 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:658 [inline]
 smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:961
 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:487
RIP: 0010:lock_is_held_type+0x21/0x280 kernel/locking/lockdep.c:3780
RSP: 0018:ffff88006b4af8c0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: 0000000000000001 RBX: ffff88006b4af7a0 RCX: 1ffff1000d695ef8
RDX: dffffc0000000000 RSI: 00000000ffffffff RDI: ffffffff8590c900
RBP: ffff88006b4af8e8 R08: ffffed000d695fde R09: ffffed000d695fde
R10: 0000000000000002 R11: ffffed000d695fdd R12: ffff88006b4afd18
R13: 0000000000000000 R14: ffffffff8590c900 R15: 0000000000000071
 </IRQ>
 lock_is_held include/linux/lockdep.h:348 [inline]
 ___might_sleep+0x5aa/0x640 kernel/sched/core.c:7748
 __might_sleep+0x95/0x1a0 kernel/sched/core.c:7739
 __might_fault+0x15b/0x290 mm/memory.c:4080
 __copy_from_user arch/x86/include/asm/uaccess_64.h:113 [inline]
 _copy_from_user+0xc1/0x120 arch/x86/lib/usercopy.c:80
 copy_from_user arch/x86/include/asm/uaccess.h:702 [inline]
 SYSC_nanosleep kernel/time/hrtimer.c:1581 [inline]
 SyS_nanosleep+0xab/0x1a0 kernel/time/hrtimer.c:1576
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x46f650
RSP: 002b:00007ffe30b79c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000046f650
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffe30b79c80
RBP: 00000000000057cd R08: 00000000000012a8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000002aa4d
R13: 00000000000057cd R14: 000000000000001f R15: 000000000002a99d
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..