From a3285aa4eecd722508dab01c4932b11b4ba80134 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Tue, 9 May 2006 10:50:29 -0700 Subject: IB/mthca: Fix race in reference counting Fix races in in destroying various objects. If a destroy routine waits for an object to become free by doing wait_event(&obj->wait, !atomic_read(&obj->refcount)); /* now clean up and destroy the object */ and another place drops a reference to the object by doing if (atomic_dec_and_test(&obj->refcount)) wake_up(&obj->wait); then this is susceptible to a race where the wait_event() and final freeing of the object occur between the atomic_dec_and_test() and the wake_up(). And this is a use-after-free, since wake_up() will be called on part of the already-freed object. Fix this in mthca by replacing the atomic_t refcounts with plain old integers protected by a spinlock. This makes it possible to do the decrement of the reference count and the wake_up() so that it appears as a single atomic operation to the code waiting on the wait queue. While touching this code, also simplify mthca_cq_clean(): the CQ being cleaned cannot go away, because it still has a QP attached to it. So there's no reason to be paranoid and look up the CQ by number; it's perfectly safe to use the pointer that the callers already have. Signed-off-by: Roland Dreier --- drivers/infiniband/hw/mthca/mthca_dev.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/infiniband/hw/mthca/mthca_dev.h') diff --git a/drivers/infiniband/hw/mthca/mthca_dev.h b/drivers/infiniband/hw/mthca/mthca_dev.h index 4c1dcb4c1822..f8160b8de090 100644 --- a/drivers/infiniband/hw/mthca/mthca_dev.h +++ b/drivers/infiniband/hw/mthca/mthca_dev.h @@ -496,7 +496,7 @@ void mthca_free_cq(struct mthca_dev *dev, void mthca_cq_completion(struct mthca_dev *dev, u32 cqn); void mthca_cq_event(struct mthca_dev *dev, u32 cqn, enum ib_event_type event_type); -void mthca_cq_clean(struct mthca_dev *dev, u32 cqn, u32 qpn, +void mthca_cq_clean(struct mthca_dev *dev, struct mthca_cq *cq, u32 qpn, struct mthca_srq *srq); void mthca_cq_resize_copy_cqes(struct mthca_cq *cq); int mthca_alloc_cq_buf(struct mthca_dev *dev, struct mthca_cq_buf *buf, int nent); -- cgit v1.2.3