linux/drivers/infiniband
Tejun Heo 74b44bbe80 RDMAVT: Fix synchronization around percpu_ref
rvt_mregion uses percpu_ref for reference counting and RCU to protect
accesses from lkey_table.  When a rvt_mregion needs to be freed, it
first gets unregistered from lkey_table and then rvt_check_refs() is
called to wait for in-flight usages before the rvt_mregion is freed.

rvt_check_refs() seems to have a couple issues.

* It has a fast exit path which tests percpu_ref_is_zero().  However,
  a percpu_ref reading zero doesn't mean that the object can be
  released.  In fact, the ->release() callback might not even have
  started executing yet.  Proceeding with freeing can lead to
  use-after-free.

* lkey_table is RCU protected but there is no RCU grace period in the
  free path.  percpu_ref uses RCU internally but it's sched-RCU whose
  grace periods are different from regular RCU.  Also, it generally
  isn't a good idea to depend on internal behaviors like this.

To address the above issues, this patch removes the fast exit and adds
an explicit synchronize_rcu().

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: linux-rdma@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
2018-03-14 12:10:18 -07:00
..
core RDMA/ucma: Check that user doesn't overflow QP state 2018-03-07 15:25:40 -05:00
hw RDMA/mlx5: Fix integer overflow while resizing CQ 2018-03-09 18:10:48 -05:00
sw RDMAVT: Fix synchronization around percpu_ref 2018-03-14 12:10:18 -07:00
ulp IB/ipoib: Do not warn if IPoIB debugfs doesn't exist 2018-02-15 14:59:43 -07:00
Kconfig Second pull request for 4.16 merge window 2018-02-06 11:09:45 -08:00
Makefile IB/rdmavt: Create module framework and handle driver registration 2016-03-10 20:37:04 -05:00