[Dapper] [CVE-2011-0695] [PATCH 1/1] IB/cm: Bump reference count on cm_id before invoking callback, CVE-2011-0695

[Leann Ogasawara]

On Mon, 2011-04-25 at 12:28 -0700, Brad Figg wrote:
> From: Sean Hefty <sean.hefty at intel.com>
> 
> CVE-2011-0695
> 
> BugLink: http://bugs.launchpad.net/bugs/770369
> 
> 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 at intel.com>
> Acked-by: Doug Ledford <dledford at redhat.com>
> Cc: <stable at kernel.org>
> Signed-off-by: Roland Dreier <roland at purestorage.com>
> 
> (backported from commit 29963437a48475036353b95ab142bf199adb909e)
> Signed-off-by: Brad Figg <brad.figg at canonical.com>

Acked-by: Leann Ogasawara <leann.ogasawara at canonical.com>

> ---
>  drivers/infiniband/core/cm.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
> index 02110e0..c777dbd 100644
> --- a/drivers/infiniband/core/cm.c
> +++ b/drivers/infiniband/core/cm.c
> @@ -2648,6 +2648,7 @@ 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_irqrestore(&cm.lock, flags);
>  
>  	cm_id_priv->id.cm_handler = cur_cm_id_priv->id.cm_handler;
> -- 
> 1.7.0.4
> 
>