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  1. 15 Mar, 2011 2 commits
    • Sean Hefty's avatar
      IB/cm: Bump reference count on cm_id before invoking callback · 29963437
      Sean Hefty authored 
      When processing a SIDR REQ, the ib_cm allocates a new cm_id.  The
refcount of the cm_id is initialized to 1.  However, cm_process_work
will decrement the refcount after invoking all callbacks.  The result
is that the cm_id will end up with refcount set to 0 by the end of the
sidr req handler.

If a user tries to destroy the cm_id, the destruction will proceed,
under the incorrect assumption that no other threads are referencing
the cm_id.  This can lead to a crash when the cm callback thread tries
to access the cm_id.

This problem was noticed as part of a larger investigation with kernel
crashes in the rdma_cm when running on a real time OS.
Signed-off-by: default avatarSean Hefty <sean.hefty@intel.com>
Acked-by: default avatarDoug Ledford <dledford@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarRoland Dreier <roland@purestorage.com>
      29963437
    • Sean Hefty's avatar
      RDMA/cma: Fix crash in request handlers · 25ae21a1
      Sean Hefty authored 
      Doug Ledford and Red Hat reported a crash when running the rdma_cm on
a real-time OS.  The crash has the following call trace:

    cm_process_work
       cma_req_handler
          cma_disable_callback
          rdma_create_id
             kzalloc
             init_completion
          cma_get_net_info
          cma_save_net_info
          cma_any_addr
             cma_zero_addr
          rdma_translate_ip
             rdma_copy_addr
          cma_acquire_dev
             rdma_addr_get_sgid
             ib_find_cached_gid
             cma_attach_to_dev
          ucma_event_handler
             kzalloc
             ib_copy_ah_attr_to_user
          cma_comp

[ preempted ]

    cma_write
        copy_from_user
        ucma_destroy_id
           copy_from_user
           _ucma_find_context
           ucma_put_ctx
           ucma_free_ctx
              rdma_destroy_id
                 cma_exch
                 cma_cancel_operation
                 rdma_node_get_transport

        rt_mutex_slowunlock
        bad_area_nosemaphore
        oops_enter

They were able to reproduce the crash multiple times with the
following details:

    Crash seems to always happen on the:
            mutex_unlock(&conn_id->handler_mutex);
    as conn_id looks to have been freed during this code path.

An examination of the code shows that a race exists in the request
handlers.  When a new connection request is received, the rdma_cm
allocates a new connection identifier.  This identifier has a single
reference count on it.  If a user calls rdma_destroy_id() from another
thread after receiving a callback, rdma_destroy_id will proceed to
destroy the id and free the associated memory.  However, the request
handlers may still be in the process of running.  When control returns
to the request handlers, they can attempt to access the newly created
identifiers.

Fix this by holding a reference on the newly created rdma_cm_id until
the request handler is through accessing it.
Signed-off-by: default avatarSean Hefty <sean.hefty@intel.com>
Acked-by: default avatarDoug Ledford <dledford@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarRoland Dreier <roland@purestorage.com>
      25ae21a1
  3. 18 Feb, 2011 8 commits
  5. 17 Feb, 2011 10 commits
  7. 16 Feb, 2011 15 commits
  9. 15 Feb, 2011 5 commits
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