From: Krishna Kumar <krkumar2@in.ibm.com>
Date: Fri, 29 Sep 2006 18:51:49 +0000 (-0700)
Subject: RDMA/cma: Fix device removal race
X-Git-Tag: v2.6.19-rc1~369^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6e35aabee125999f4b3c01326f5339fa74a89259;p=pandora-kernel.git

RDMA/cma: Fix device removal race

The race is as follows:

A process : cma_process_remove() calls cma_remove_id_dev(),
	    which sets id state to CMA_DEVICE_REMOVAL and
	    calls wait_event(dev_remove).

B process : cma_req_handler() had incremented dev_remove,
	    and calls cma_acquire_ib_dev() and on failure
	    calls cma_release_remove(), which does a
	    wake_up of cma_process_remove(). Then
	    cma_req_handler() calls rdma_destroy_id();

A Process : cma_remove_id_dev() gets woken and checks the
	    state of id, and since it is still (wrongly)
	    CMA_DEVICE_REMOVAL, it calls notify_user(id)
	    and if that fails, the caller - cma_process_remove()
	    calls rdma_destroy_id(id). Two processes can
	    call rdma_destroy_id(), resulting in one
	    de-referencing kfreed id_priv.

Fix is for process B to set CMA_DESTROYING in cma_req_handler()
so that process A will return instead of doing a rdma_destroy_id().

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
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