Subject: possible deadlock in rtnl_lock (2)

From: syzbot <[email-masked]>
Date: Thu, 01 Feb 2018 10:58:01 -0800

Hello,

syzbot hit the following crash on upstream commit
255442c93843f52b6891b21d0b485bf2c97f93c3 (Thu Feb 1 03:25:25 2018 +0000)
Merge tag 'docs-4.16' of git://git.lwn.net/linux

So far this crash happened 1587 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: [email-masked]
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======================================================
WARNING: possible circular locking dependency detected
4.15.0+ #290 Not tainted
------------------------------------------------------
syzkaller681093/4124 is trying to acquire lock:
  (rtnl_mutex){+.+.}, at: [<00000000c3d62391>] rtnl_lock+0x17/0x20  
net/core/rtnetlink.c:74

but task is already holding lock:
  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>] lock_sock  
include/net/sock.h:1461 [inline]
  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>] ip_setsockopt+0x8c/0xb0  
net/ipv4/ip_sockglue.c:1259

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_INET){+.+.}:
        lock_sock_nested+0xc2/0x110 net/core/sock.c:2780
        lock_sock include/net/sock.h:1461 [inline]
        do_ip_getsockopt+0x1b3/0x2170 net/ipv4/ip_sockglue.c:1335
        ip_getsockopt+0x90/0x220 net/ipv4/ip_sockglue.c:1566
        tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359
        sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2937
        SYSC_getsockopt net/socket.c:1880 [inline]
        SyS_getsockopt+0x178/0x340 net/socket.c:1862
        entry_SYSCALL_64_fastpath+0x29/0xa0

-> #0 (rtnl_mutex){+.+.}:
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
        __mutex_lock_common kernel/locking/mutex.c:756 [inline]
        __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
        mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
        rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
        register_netdevice_notifier+0xad/0x860 net/core/dev.c:1607
        tee_tg_check+0x1a0/0x280 net/netfilter/xt_TEE.c:106
        xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:845
        check_target net/ipv4/netfilter/ip_tables.c:513 [inline]
        find_check_entry.isra.8+0x8c8/0xcb0  
net/ipv4/netfilter/ip_tables.c:554
        translate_table+0xed1/0x1610 net/ipv4/netfilter/ip_tables.c:725
        do_replace net/ipv4/netfilter/ip_tables.c:1141 [inline]
        do_ipt_set_ctl+0x370/0x5f0 net/ipv4/netfilter/ip_tables.c:1675
        nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
        nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
        ip_setsockopt+0xa1/0xb0 net/ipv4/ip_sockglue.c:1260
        sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4104
        sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
        SYSC_setsockopt net/socket.c:1849 [inline]
        SyS_setsockopt+0x189/0x360 net/socket.c:1828
        entry_SYSCALL_64_fastpath+0x29/0xa0

other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(sk_lock-AF_INET);
                                lock(rtnl_mutex);
                                lock(sk_lock-AF_INET);
   lock(rtnl_mutex);

  *** DEADLOCK ***

1 lock held by syzkaller681093/4124:
  #0:  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>] lock_sock  
include/net/sock.h:1461 [inline]
  #0:  (sk_lock-AF_INET){+.+.}, at: [<0000000051813e83>]  
ip_setsockopt+0x8c/0xb0 net/ipv4/ip_sockglue.c:1259

stack backtrace:
CPU: 0 PID: 4124 Comm: syzkaller681093 Not tainted 4.15.0+ #290
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+0x194/0x257 lib/dump_stack.c:53
  print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223
  check_prev_add kernel/locking/lockdep.c:1863 [inline]
  check_prevs_add kernel/locking/lockdep.c:1976 [inline]
  validate_chain kernel/locking/lockdep.c:2417 [inline]
  __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431
  lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
  __mutex_lock_common kernel/locking/mutex.c:756 [inline]
  __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
  rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
  register_netdevice_notifier+0xad/0x860 net/core/dev.c:1607
  tee_tg_check+0x1a0/0x280 net/netfilter/xt_TEE.c:106
  xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:845
  check_target net/ipv4/netfilter/ip_tables.c:513 [inline]
  find_check_entry.isra.8+0x8c8/0xcb0 net/ipv4/netfilter/ip_tables.c:554
  translate_table+0xed1/0x1610 net/ipv4/netfilter/ip_tables.c:725
  do_replace net/ipv4/netfilter/ip_tables.c:1141 [inline]
  do_ipt_set_ctl+0x370/0x5f0 net/ipv4/netfilter/ip_tables.c:1675
  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
  nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
  ip_setsockopt+0xa1/0xb0 net/ipv4/ip_sockglue.c:1260
  sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4104
  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
  SYSC_setsockopt net/socket.c:1849 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1828
  entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x445bd9
RSP: 002b:00007fffdfb6a998 EFLAGS: 00000203 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000445bd9
RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fffdfb6aa48 R08: 0000000000000318 R09: 0000000000000000
R10: 000000002

---
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