• Eric Dumazet's avatar
    bpf: fix lockdep splat · 89ad2fa3
    Eric Dumazet authored
    pcpu_freelist_pop() needs the same lockdep awareness than
    pcpu_freelist_populate() to avoid a false positive.
    
     [ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ]
    
     switchto-defaul/12508 [HC0[0]:SC0[6]:HE0:SE0] is trying to acquire:
      (&htab->buckets[i].lock){......}, at: [<ffffffff9dc099cb>] __htab_percpu_map_update_elem+0x1cb/0x300
    
     and this task is already holding:
      (dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...}, at: [<ffffffff9e135848>] __dev_queue_xmit+0
    x868/0x1240
     which would create a new lock dependency:
      (dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...} -> (&htab->buckets[i].lock){......}
    
     but this new dependency connects a SOFTIRQ-irq-safe lock:
      (dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...}
     ... which became SOFTIRQ-irq-safe at:
       [<ffffffff9db5931b>] __lock_acquire+0x42b/0x1f10
       [<ffffffff9db5b32c>] lock_acquire+0xbc/0x1b0
       [<ffffffff9da05e38>] _raw_spin_lock+0x38/0x50
       [<ffffffff9e135848>] __dev_queue_xmit+0x868/0x1240
       [<ffffffff9e136240>] dev_queue_xmit+0x10/0x20
       [<ffffffff9e1965d9>] ip_finish_output2+0x439/0x590
       [<ffffffff9e197410>] ip_finish_output+0x150/0x2f0
       [<ffffffff9e19886d>] ip_output+0x7d/0x260
       [<ffffffff9e19789e>] ip_local_out+0x5e/0xe0
       [<ffffffff9e197b25>] ip_queue_xmit+0x205/0x620
       [<ffffffff9e1b8398>] tcp_transmit_skb+0x5a8/0xcb0
       [<ffffffff9e1ba152>] tcp_write_xmit+0x242/0x1070
       [<ffffffff9e1baffc>] __tcp_push_pending_frames+0x3c/0xf0
       [<ffffffff9e1b3472>] tcp_rcv_established+0x312/0x700
       [<ffffffff9e1c1acc>] tcp_v4_do_rcv+0x11c/0x200
       [<ffffffff9e1c3dc2>] tcp_v4_rcv+0xaa2/0xc30
       [<ffffffff9e191107>] ip_local_deliver_finish+0xa7/0x240
       [<ffffffff9e191a36>] ip_local_deliver+0x66/0x200
       [<ffffffff9e19137d>] ip_rcv_finish+0xdd/0x560
       [<ffffffff9e191e65>] ip_rcv+0x295/0x510
       [<ffffffff9e12ff88>] __netif_receive_skb_core+0x988/0x1020
       [<ffffffff9e130641>] __netif_receive_skb+0x21/0x70
       [<ffffffff9e1306ff>] process_backlog+0x6f/0x230
       [<ffffffff9e132129>] net_rx_action+0x229/0x420
       [<ffffffff9da07ee8>] __do_softirq+0xd8/0x43d
       [<ffffffff9e282bcc>] do_softirq_own_stack+0x1c/0x30
       [<ffffffff9dafc2f5>] do_softirq+0x55/0x60
       [<ffffffff9dafc3a8>] __local_bh_enable_ip+0xa8/0xb0
       [<ffffffff9db4c727>] cpu_startup_entry+0x1c7/0x500
       [<ffffffff9daab333>] start_secondary+0x113/0x140
    
     to a SOFTIRQ-irq-unsafe lock:
      (&head->lock){+.+...}
     ... which became SOFTIRQ-irq-unsafe at:
     ...  [<ffffffff9db5971f>] __lock_acquire+0x82f/0x1f10
       [<ffffffff9db5b32c>] lock_acquire+0xbc/0x1b0
       [<ffffffff9da05e38>] _raw_spin_lock+0x38/0x50
       [<ffffffff9dc0b7fa>] pcpu_freelist_pop+0x7a/0xb0
       [<ffffffff9dc08b2c>] htab_map_alloc+0x50c/0x5f0
       [<ffffffff9dc00dc5>] SyS_bpf+0x265/0x1200
       [<ffffffff9e28195f>] entry_SYSCALL_64_fastpath+0x12/0x17
    
     other info that might help us debug this:
    
     Chain exists of:
       dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2 --> &htab->buckets[i].lock --> &head->lock
    
      Possible interrupt unsafe locking scenario:
    
            CPU0                    CPU1
            ----                    ----
       lock(&head->lock);
                                    local_irq_disable();
                                    lock(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2);
                                    lock(&htab->buckets[i].lock);
       <Interrupt>
         lock(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2);
    
      *** DEADLOCK ***
    
    Fixes: e19494ed ("bpf: introduce percpu_freelist")
    Signed-off-by: 's avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    89ad2fa3
percpu_freelist.c 2.35 KB