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IB/cm: Bump reference count on cm_id before invoking callback

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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: Sean Hefty <[email protected]>
Acked-by: Doug Ledford <[email protected]>
Cc: <[email protected]>
Signed-off-by: Roland Dreier <[email protected]>
This commit is contained in:
Sean Hefty 2011-02-23 08:17:40 -08:00 • committed by Roland Dreier
commit 29963437a4
1 changed files with 1 additions and 0 deletions
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1
drivers/infiniband/core/cm.c
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@ -2989,6 +2989,7 @@ static int cm_sidr_req_handler(struct cm_work *work)
goto out; /* No match. */
}
atomic_inc(&cur_cm_id_priv->refcount);
atomic_inc(&cm_id_priv->refcount);
spin_unlock_irq(&cm.lock);
cm_id_priv->id.cm_handler = cur_cm_id_priv->id.cm_handler;