• Eric W. Biederman's avatar
    ipv4: Avoid crashing in ip_error · 381c759d
    Eric W. Biederman authored
    ip_error does not check if in_dev is NULL before dereferencing it.
    
    IThe following sequence of calls is possible:
    CPU A                          CPU B
    ip_rcv_finish
        ip_route_input_noref()
            ip_route_input_slow()
                                   inetdev_destroy()
        dst_input()
    
    With the result that a network device can be destroyed while processing
    an input packet.
    
    A crash was triggered with only unicast packets in flight, and
    forwarding enabled on the only network device.   The error condition
    was created by the removal of the network device.
    
    As such it is likely the that error code was -EHOSTUNREACH, and the
    action taken by ip_error (if in_dev had been accessible) would have
    been to not increment any counters and to have tried and likely failed
    to send an icmp error as the network device is going away.
    
    Therefore handle this weird case by just dropping the packet if
    !in_dev.  It will result in dropping the packet sooner, and will not
    result in an actual change of behavior.
    
    Fixes: 251da413 ("ipv4: Cache ip_error() routes even when not forwarding.")
    Reported-by: default avatarVittorio Gambaletta <linuxbugs@vittgam.net>
    Tested-by: default avatarVittorio Gambaletta <linuxbugs@vittgam.net>
    Signed-off-by: default avatarVittorio Gambaletta <linuxbugs@vittgam.net>
    Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    Acked-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    381c759d
route.c 67.1 KB