Date:   Mon, 28 May 2018 16:16:02 -0700
From:   syzbot <syzbot+83bdee62c80cc044cb1a@...kaller.appspotmail.com>
To:     ast@...nel.org, daniel@...earbox.net, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: possible deadlock in sock_hash_free

Hello,

syzbot found the following crash on:

HEAD commit:    7a1a98c171ea Merge branch 'bpf-sendmsg-hook'
git tree:       bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=131f4067800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
dashboard link: https://syzkaller.appspot.com/bug?extid=83bdee62c80cc044cb1a
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=17a0be2f800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=164cf10f800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+83bdee62c80cc044cb1a@...kaller.appspotmail.com


======================================================
WARNING: possible circular locking dependency detected
4.17.0-rc6+ #25 Not tainted
------------------------------------------------------
kworker/1:0/18 is trying to acquire lock:
00000000ef3a7ff3 (clock-AF_INET6){++..}, at: sock_hash_free+0x377/0x700  
kernel/bpf/sockmap.c:2089

but task is already holding lock:
00000000989798b8 (&htab->buckets[i].lock){+...}, at:  
sock_hash_free+0x1d4/0x700 kernel/bpf/sockmap.c:2083

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&htab->buckets[i].lock){+...}:
        __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
        _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168
        bpf_tcp_close+0x822/0x10b0 kernel/bpf/sockmap.c:285
        inet_release+0x104/0x1f0 net/ipv4/af_inet.c:427
        inet6_release+0x50/0x70 net/ipv6/af_inet6.c:459
        sock_release+0x96/0x1b0 net/socket.c:594
        sock_close+0x16/0x20 net/socket.c:1149
        __fput+0x34d/0x890 fs/file_table.c:209
        ____fput+0x15/0x20 fs/file_table.c:243
        task_work_run+0x1e4/0x290 kernel/task_work.c:113
        exit_task_work include/linux/task_work.h:22 [inline]
        do_exit+0x1aee/0x2730 kernel/exit.c:865
        do_group_exit+0x16f/0x430 kernel/exit.c:968
        __do_sys_exit_group kernel/exit.c:979 [inline]
        __se_sys_exit_group kernel/exit.c:977 [inline]
        __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977
        do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (clock-AF_INET6){++..}:
        lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920
        __raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline]
        _raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:312
        sock_hash_free+0x377/0x700 kernel/bpf/sockmap.c:2089
        bpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:261
        process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
        worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
        kthread+0x345/0x410 kernel/kthread.c:240
        ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&htab->buckets[i].lock);
                                lock(clock-AF_INET6);
                                lock(&htab->buckets[i].lock);
   lock(clock-AF_INET6);

  *** DEADLOCK ***

4 locks held by kworker/1:0/18:
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at:  
__write_once_size include/linux/compiler.h:215 [inline]
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at:  
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at: atomic64_set  
include/asm-generic/atomic-instrumented.h:40 [inline]
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at: atomic_long_set  
include/asm-generic/atomic-long.h:57 [inline]
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at: set_work_data  
kernel/workqueue.c:617 [inline]
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at:  
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
  #0: 00000000b569d373 ((wq_completion)"events"){+.+.}, at:  
process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
  #1: 0000000041d1b332 ((work_completion)(&map->work)){+.+.}, at:  
process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
  #2: 00000000da1a504c (rcu_read_lock){....}, at: sock_hash_free+0x0/0x700  
include/net/sock.h:2178
  #3: 00000000989798b8 (&htab->buckets[i].lock){+...}, at:  
sock_hash_free+0x1d4/0x700 kernel/bpf/sockmap.c:2083

stack backtrace:
CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 4.17.0-rc6+ #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events bpf_map_free_deferred
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  print_circular_bug.isra.36.cold.54+0x1bd/0x27d  
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+0x343e/0x5140 kernel/locking/lockdep.c:3431
  lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920
  __raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline]
  _raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:312
  sock_hash_free+0x377/0x700 kernel/bpf/sockmap.c:2089
  bpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:261
  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
  kthread+0x345/0x410 kernel/kthread.c:240
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412


---
This bug is generated by a bot. It may contain errors.
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