• Eric Dumazet's avatar
    net: fix sock_wake_async() rcu protection · ceb5d58b
    Eric Dumazet authored
    Dmitry provided a syzkaller (http://github.com/google/syzkaller
    
    )
    triggering a fault in sock_wake_async() when async IO is requested.
    
    Said program stressed af_unix sockets, but the issue is generic
    and should be addressed in core networking stack.
    
    The problem is that by the time sock_wake_async() is called,
    we should not access the @flags field of 'struct socket',
    as the inode containing this socket might be freed without
    further notice, and without RCU grace period.
    
    We already maintain an RCU protected structure, "struct socket_wq"
    so moving SOCKWQ_ASYNC_NOSPACE & SOCKWQ_ASYNC_WAITDATA into it
    is the safe route.
    
    It also reduces number of cache lines needing dirtying, so might
    provide a performance improvement anyway.
    
    In followup patches, we might move remaining flags (SOCK_NOSPACE,
    SOCK_PASSCRED, SOCK_PASSSEC) to save 8 bytes and let 'struct socket'
    being mostly read and let it being shared between cpus.
    Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    ceb5d58b