IB/cm: Bump reference count on cm_id before invoking callback, CVE-2011-0695
On Mon, 2011-04-25 at 12:28 -0700, Brad Figg wrote:
> From: Sean Hefty <firstname.lastname@example.org>
> 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 <email@example.com>
> Acked-by: Doug Ledford <firstname.lastname@example.org>
> Cc: <email@example.com>
> Signed-off-by: Roland Dreier <firstname.lastname@example.org>
> (backported from commit 29963437a48475036353b95ab142bf199adb909e)
> Signed-off-by: Brad Figg <email@example.com>