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Date:   Mon, 13 Aug 2018 06:33:02 -0700
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Subject: Re: general protection fault in send_sigurg_to_task
From:   syzbot <syzbot+1f371ca19b341a276761@syzkaller.appspotmail.com>
To:     bfields@fieldses.org, jlayton@kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk
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syzbot has found a reproducer for the following crash on:

HEAD commit:    5ed5da74de9e Add linux-next specific files for 20180813
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10787028400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=18edf0289d1b5ab
dashboard link: https://syzkaller.appspot.com/bug?extid=1f371ca19b341a276761
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1487e828400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15084b72400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1f371ca19b341a276761@syzkaller.appspotmail.com

nf_conntrack: default automatic helper assignment has been turned off for  
security reasons and CT-based  firewall rule not found. Use the iptables CT  
target to attach helpers instead.
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: 1 PID: 4474 Comm: syz-executor782 Not tainted 4.18.0-next-20180813+ #37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:sigio_perm fs/fcntl.c:715 [inline]
RIP: 0010:send_sigurg_to_task+0xf5/0x4d0 fs/fcntl.c:810
Code: 61 af b1 ff 45 84 f6 0f 84 52 03 00 00 e8 83 ae b1 ff 49 8d bf 58 06  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 91 03 00 00 48 8d 43 c0 4d 8b b7 58 06 00 00 48
RSP: 0000:ffff8801db106c18 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8801db106c88 RCX: ffffffff81cae2d0
RDX: 00000000000000cb RSI: ffffffff81cadf6d RDI: 0000000000000658
RBP: ffff8801db106cb0 R08: ffff8801b4ad4640 R09: ffffed003b6246d6
R10: ffffed003b6246d6 R11: ffff8801db1236b3 R12: 1ffff1003b620d85
R13: ffff8801b4cb9388 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000949880(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000400bc3 CR3: 00000001bb122000 CR4: 00000000001406e0
Call Trace:
  <IRQ>
  send_sigurg+0x342/0x480 fs/fcntl.c:833
  sk_send_sigurg+0xd2/0x3d0 net/core/sock.c:2731
  tcp_check_urg net/ipv4/tcp_input.c:5266 [inline]
  tcp_urg+0x3c3/0xba0 net/ipv4/tcp_input.c:5307
  tcp_rcv_established+0xd45/0x2130 net/ipv4/tcp_input.c:5637
  tcp_v4_do_rcv+0x635/0x8f0 net/ipv4/tcp_ipv4.c:1532
  tcp_v4_rcv+0x2ff9/0x3a90 net/ipv4/tcp_ipv4.c:1824
  ip_local_deliver_finish+0x2eb/0xda0 net/ipv4/ip_input.c:215
  NF_HOOK include/linux/netfilter.h:287 [inline]
  ip_local_deliver+0x1e9/0x750 net/ipv4/ip_input.c:256
  dst_input include/net/dst.h:450 [inline]
  ip_rcv_finish+0x1f9/0x300 net/ipv4/ip_input.c:415
  NF_HOOK include/linux/netfilter.h:287 [inline]
  ip_rcv+0xed/0x610 net/ipv4/ip_input.c:524
  __netif_receive_skb_one_core+0x14d/0x200 net/core/dev.c:4892
  __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:5002
  process_backlog+0x219/0x760 net/core/dev.c:5808
  napi_poll net/core/dev.c:6228 [inline]
  net_rx_action+0x799/0x1900 net/core/dev.c:6294
  __do_softirq+0x2e8/0xa6d kernel/softirq.c:292
  invoke_softirq kernel/softirq.c:372 [inline]
  irq_exit+0x1d4/0x210 kernel/softirq.c:412
  exiting_irq arch/x86/include/asm/apic.h:527 [inline]
  smp_apic_timer_interrupt+0x186/0x690 arch/x86/kernel/apic/apic.c:1055
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
  </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783  
[inline]
RIP: 0010:lock_is_held_type+0x18b/0x210 kernel/locking/lockdep.c:3941
Code: ff df 41 c7 84 24 3c 08 00 00 00 00 00 00 48 89 fa 48 c1 ea 03 80 3c  
02 00 75 63 48 83 3d f4 33 93 06 00 74 30 48 89 df 57 9d <0f> 1f 44 00 00  
48 83 c4 08 44 89 e8 5b 41 5c 41 5d 5d c3 48 83 c4
RSP: 0000:ffff8801c6de7578 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 0000000000000286 RCX: 0000000000000000
RDX: 1ffffffff0fe3665 RSI: 0000000000000000 RDI: 0000000000000286
RBP: ffff8801c6de7598 R08: ffffed003b6246d7 R09: ffffed003b6246d6
R10: ffffed003b6246d6 R11: ffff8801db1236b3 R12: ffff8801b4ad4640
R13: 0000000000000001 R14: dffffc0000000000 R15: 0000000000000000
  lock_is_held include/linux/lockdep.h:344 [inline]
  rcu_read_lock_held+0xa9/0xc0 kernel/rcu/update.c:285
  xa_entry include/linux/xarray.h:486 [inline]
  xas_next_entry include/linux/xarray.h:905 [inline]
  filemap_map_pages+0xdab/0x1990 mm/filemap.c:2536
  do_fault_around mm/memory.c:3603 [inline]
  do_read_fault mm/memory.c:3637 [inline]
  do_fault mm/memory.c:3742 [inline]
  handle_pte_fault mm/memory.c:3973 [inline]
  __handle_mm_fault+0x339c/0x4470 mm/memory.c:4097
  handle_mm_fault+0x53e/0xc80 mm/memory.c:4134
  __do_page_fault+0x620/0xe50 arch/x86/mm/fault.c:1395
  do_page_fault+0xf6/0x7a4 arch/x86/mm/fault.c:1470
  page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1164
RIP: 0033:0x400bc3
Code: 09 00 00 00 e8 0e 09 04 00 48 c7 05 2b 2b 2d 00 00 00 00 00 48 83 c4  
10 e8 fa f1 03 00 85 c0 0f 85 d2 07 00 00 e8 ed f1 03 00 <89> c3 89 c5 85  
c0 79 0a bf 01 00 00 00 e8 6b ed 00 00 85 c0 0f 85
RSP: 002b:00007ffd6e71ae70 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 000000000000116b RCX: 000000000043fe8a
RDX: 0000001899a3a3ae RSI: 0000000000000000 RDI: 0000000001200011
RBP: 000000000000116b R08: 0000000000001149 R09: 0000000000949880
R10: 0000000000949b50 R11: 0000000000000246 R12: 000000000000a5e7
R13: 00000000004023f0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
Dumping ftrace buffer:
    (ftrace buffer empty)
---[ end trace b74ebc04d71b9f0f ]---
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:sigio_perm fs/fcntl.c:715 [inline]
RIP: 0010:send_sigurg_to_task+0xf5/0x4d0 fs/fcntl.c:810
Code: 61 af b1 ff 45 84 f6 0f 84 52 03 00 00 e8 83 ae b1 ff 49 8d bf 58 06  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 91 03 00 00 48 8d 43 c0 4d 8b b7 58 06 00 00 48
RSP: 0000:ffff8801db106c18 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8801db106c88 RCX: ffffffff81cae2d0
RDX: 00000000000000cb RSI: ffffffff81cadf6d RDI: 0000000000000658
RBP: ffff8801db106cb0 R08: ffff8801b4ad4640 R09: ffffed003b6246d6
R10: ffffed003b6246d6 R11: ffff8801db1236b3 R12: 1ffff1003b620d85
R13: ffff8801b4cb9388 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000949880(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000400bc3 CR3: 00000001bb122000 CR4: 00000000001406e0