| From | Andi Kleen <> | Subject | [PATCH] [196/275] IB/cm: Bump reference count on cm_id before invoking callback | Date | Wed, 30 Mar 2011 14:07:20 -0700 (PDT) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Sean Hefty <sean.hefty@intel.com>
commit 29963437a48475036353b95ab142bf199adb909e upstream.
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 <sean.hefty@intel.com> Acked-by: Doug Ledford <dledford@redhat.com> Signed-off-by: Roland Dreier <roland@purestorage.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Andi Kleen <ak@linux.intel.com>
--- drivers/infiniband/core/cm.c | 1 + 1 file changed, 1 insertion(+)
Index: linux-2.6.35.y/drivers/infiniband/core/cm.c =================================================================== --- linux-2.6.35.y.orig/drivers/infiniband/core/cm.c 2011-03-29 22:50:42.296176166 -0700 +++ linux-2.6.35.y/drivers/infiniband/core/cm.c 2011-03-29 23:03:02.367239599 -0700 @@ -2987,6 +2987,7 @@ 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;
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