Subject: suspicious RCU usage at ./include/net/sock.h:LINE

From: syzbot <[email-masked]>
Date: Fri, 27 Oct 2017 01:24:01 -0700

Hello,

syzkaller hit the following crash on  
c6be5a0e3cebc145127d46a58350e05d2bcf6323
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.

=============================
WARNING: suspicious RCU usage
4.13.0-next-20170907+ #17 Not tainted
-----------------------------
sctp: [Deprecated]: syz-executor3 (pid 4299) Use of struct sctp_assoc_value  
in delayed_ack socket option.
Use struct sctp_sack_info instead
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4316 at ./include/net/sock.h:1505 sock_owned_by_me  
include/net/sock.h:1505 [inline]
WARNING: CPU: 0 PID: 4316 at ./include/net/sock.h:1505 sock_owned_by_user  
include/net/sock.h:1511 [inline]
WARNING: CPU: 0 PID: 4316 at ./include/net/sock.h:1505  
strp_data_ready+0x2b7/0x390 net/strparser/strparser.c:404
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4316 Comm: syz-executor4 Not tainted 4.13.0-next-20170907+ #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:16 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:52
  panic+0x1e4/0x417 kernel/panic.c:181
  __warn+0x1c4/0x1d9 kernel/panic.c:542
  report_bug+0x211/0x2d0 lib/bug.c:183
  fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
  do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
  do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
  do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
  invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:sock_owned_by_me include/net/sock.h:1505 [inline]
RIP: 0010:sock_owned_by_user include/net/sock.h:1511 [inline]
RIP: 0010:strp_data_ready+0x2b7/0x390 net/strparser/strparser.c:404
RSP: 0018:ffff8801d9a37980 EFLAGS: 00010216
RAX: 0000000000010000 RBX: ffff8801d9ab7748 RCX: ffffc90003ef3000
RDX: 00000000000001ef RSI: ffffffff846b14c7 RDI: ffffffff85cc1020
RBP: ffff8801d9a379a0 R08: 0000000000000000 R09: 0000000000000001
R10: ffff8801d9a37120 R11: ffffffff8705fca0 R12: ffff8801d8e7a000
R13: ffff8801d9ab7750 R14: ffff8801d9a37b08 R15: ffff8801d8e7a000
  psock_data_ready+0x56/0x70 net/kcm/kcmsock.c:353
  unix_dgram_sendmsg+0xa77/0x1600 net/unix/af_unix.c:1808
  unix_seqpacket_sendmsg+0xf3/0x160 net/unix/af_unix.c:2062
  sock_sendmsg_nosec net/socket.c:633 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:643
  sock_write_iter+0x320/0x5e0 net/socket.c:912
  call_write_iter include/linux/fs.h:1744 [inline]
  new_sync_write fs/read_write.c:457 [inline]
  __vfs_write+0x68a/0x970 fs/read_write.c:470
  vfs_write+0x18f/0x510 fs/read_write.c:518
  SYSC_write fs/read_write.c:565 [inline]
  SyS_write+0xef/0x220 fs/read_write.c:557
  entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x451e59
RSP: 002b:00007f370bc06c08 EFLAGS: 00000216 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000718160 RCX: 0000000000451e59
RDX: 000000000000009a RSI: 0000000020ef4000 RDI: 0000000000000005
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004bda78
R13: 00000000ffffffff R14: 000000000000001b R15: 0000000000000006
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

---
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