• Sowmini Varadhan's avatar
    rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and... · ebeeb1ad
    Sowmini Varadhan authored
    rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and rds connection/workq management
    
    An rds_connection can get added during netns deletion between lines 528
    and 529 of
    
      506 static void rds_tcp_kill_sock(struct net *net)
      :
      /* code to pull out all the rds_connections that should be destroyed */
      :
      528         spin_unlock_irq(&rds_tcp_conn_lock);
      529         list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)
      530                 rds_conn_destroy(tc->t_cpath->cp_conn);
    
    Such an rds_connection would miss out the rds_conn_destroy()
    loop (that cancels all pending work) and (if it was scheduled
    after netns deletion) could trigger the use-after-free.
    
    A similar race-window exists for the module unload path
    in rds_tcp_exit -> rds_tcp_destroy_conns
    
    Concurrency with netns deletion (rds_tcp_kill_sock()) must be handled
    by checking check_net() before enqueuing new work or adding new
    connections.
    
    Concurrency with module-unload is handled by maintaining a module
    specific flag that is set at the start of the module exit function,
    and must be checked before enqueuing new work or adding new connections.
    
    This commit refactors existing RDS_DESTROY_PENDING checks added by
    commit 3db6e0d1 ("rds: use RCU to synchronize work-enqueue with
    connection teardown") and consolidates all the concurrency checks
    listed above into the function rds_destroy_pending().
    Signed-off-by: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
    Acked-by: default avatarSantosh Shilimkar <santosh.shilimkar@oracle.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    ebeeb1ad
threads.c 7.81 KB