• Sabrina Dubroca's avatar
    e1000: add dummy allocator to fix race condition between mtu change and netpoll · 08e83316
    Sabrina Dubroca authored
    There is a race condition between e1000_change_mtu's cleanups and
    netpoll, when we change the MTU across jumbo size:
    
    Changing MTU frees all the rx buffers:
        e1000_change_mtu -> e1000_down -> e1000_clean_all_rx_rings ->
            e1000_clean_rx_ring
    
    Then, close to the end of e1000_change_mtu:
        pr_info -> ... -> netpoll_poll_dev -> e1000_clean ->
            e1000_clean_rx_irq -> e1000_alloc_rx_buffers -> e1000_alloc_frag
    
    And when we come back to do the rest of the MTU change:
        e1000_up -> e1000_configure -> e1000_configure_rx ->
            e1000_alloc_jumbo_rx_buffers
    
    alloc_jumbo finds the buffers already != NULL, since data (shared with
    page in e1000_rx_buffer->rxbuf) has been re-alloc'd, but it's garbage,
    or at least not what is expected when in jumbo state.
    
    This results in an unusable adapter (packets don't get through), and a
    NULL pointer dereference on the next call to e1000_clean_rx_ring
    (other mtu change, link down, shutdown):
    
    BUG: unable to handle kernel NULL pointer dereference at           (null)
    IP: [<ffffffff81194d6e>] put_compound_page+0x7e/0x330
    
        [...]
    
    Call Trace:
     [<ffffffff81195445>] put_page+0x55/0x60
     [<ffffffff815d9f44>] e1000_clean_rx_ring+0x134/0x200
     [<ffffffff815da055>] e1000_clean_all_rx_rings+0x45/0x60
     [<ffffffff815df5e0>] e1000_down+0x1c0/0x1d0
     [<ffffffff811e2260>] ? deactivate_slab+0x7f0/0x840
     [<ffffffff815e21bc>] e1000_change_mtu+0xdc/0x170
     [<ffffffff81647050>] dev_set_mtu+0xa0/0x140
     [<ffffffff81664218>] do_setlink+0x218/0xac0
     [<ffffffff814459e9>] ? nla_parse+0xb9/0x120
     [<ffffffff816652d0>] rtnl_newlink+0x6d0/0x890
     [<ffffffff8104f000>] ? kvm_clock_read+0x20/0x40
     [<ffffffff810a2068>] ? sched_clock_cpu+0xa8/0x100
     [<ffffffff81663802>] rtnetlink_rcv_msg+0x92/0x260
    
    By setting the allocator to a dummy version, netpoll can't mess up our
    rx buffers.  The allocator is set back to a sane value in
    e1000_configure_rx.
    
    Fixes: edbbb3ca ("e1000: implement jumbo receive with partial descriptors")
    Signed-off-by: default avatarSabrina Dubroca <sd@queasysnail.net>
    Tested-by: default avatarAaron Brown <aaron.f.brown@intel.com>
    Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
    08e83316
e1000_main.c 146 KB