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 <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/mthca/mthca_cq.c b/drivers/infiniband/hw/mthca/mthca_cq.c
index 312cf90..205854e 100644
--- a/drivers/infiniband/hw/mthca/mthca_cq.c
+++ b/drivers/infiniband/hw/mthca/mthca_cq.c
@@ -238,9 +238,9 @@
spin_lock(&dev->cq_table.lock);
cq = mthca_array_get(&dev->cq_table.cq, cqn & (dev->limits.num_cqs - 1));
-
if (cq)
- atomic_inc(&cq->refcount);
+ ++cq->refcount;
+
spin_unlock(&dev->cq_table.lock);
if (!cq) {
@@ -254,8 +254,10 @@
if (cq->ibcq.event_handler)
cq->ibcq.event_handler(&event, cq->ibcq.cq_context);
- if (atomic_dec_and_test(&cq->refcount))
+ spin_lock(&dev->cq_table.lock);
+ if (!--cq->refcount)
wake_up(&cq->wait);
+ spin_unlock(&dev->cq_table.lock);
}
static inline int is_recv_cqe(struct mthca_cqe *cqe)
@@ -267,23 +269,13 @@
return !(cqe->is_send & 0x80);
}
-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)
{
- struct mthca_cq *cq;
struct mthca_cqe *cqe;
u32 prod_index;
int nfreed = 0;
- spin_lock_irq(&dev->cq_table.lock);
- cq = mthca_array_get(&dev->cq_table.cq, cqn & (dev->limits.num_cqs - 1));
- if (cq)
- atomic_inc(&cq->refcount);
- spin_unlock_irq(&dev->cq_table.lock);
-
- if (!cq)
- return;
-
spin_lock_irq(&cq->lock);
/*
@@ -301,7 +293,7 @@
if (0)
mthca_dbg(dev, "Cleaning QPN %06x from CQN %06x; ci %d, pi %d\n",
- qpn, cqn, cq->cons_index, prod_index);
+ qpn, cq->cqn, cq->cons_index, prod_index);
/*
* Now sweep backwards through the CQ, removing CQ entries
@@ -325,8 +317,6 @@
}
spin_unlock_irq(&cq->lock);
- if (atomic_dec_and_test(&cq->refcount))
- wake_up(&cq->wait);
}
void mthca_cq_resize_copy_cqes(struct mthca_cq *cq)
@@ -821,7 +811,7 @@
}
spin_lock_init(&cq->lock);
- atomic_set(&cq->refcount, 1);
+ cq->refcount = 1;
init_waitqueue_head(&cq->wait);
memset(cq_context, 0, sizeof *cq_context);
@@ -896,6 +886,17 @@
return err;
}
+static inline int get_cq_refcount(struct mthca_dev *dev, struct mthca_cq *cq)
+{
+ int c;
+
+ spin_lock_irq(&dev->cq_table.lock);
+ c = cq->refcount;
+ spin_unlock_irq(&dev->cq_table.lock);
+
+ return c;
+}
+
void mthca_free_cq(struct mthca_dev *dev,
struct mthca_cq *cq)
{
@@ -929,6 +930,7 @@
spin_lock_irq(&dev->cq_table.lock);
mthca_array_clear(&dev->cq_table.cq,
cq->cqn & (dev->limits.num_cqs - 1));
+ --cq->refcount;
spin_unlock_irq(&dev->cq_table.lock);
if (dev->mthca_flags & MTHCA_FLAG_MSI_X)
@@ -936,8 +938,7 @@
else
synchronize_irq(dev->pdev->irq);
- atomic_dec(&cq->refcount);
- wait_event(cq->wait, !atomic_read(&cq->refcount));
+ wait_event(cq->wait, !get_cq_refcount(dev, cq));
if (cq->is_kernel) {
mthca_free_cq_buf(dev, &cq->buf, cq->ibcq.cqe);
diff --git a/drivers/infiniband/hw/mthca/mthca_dev.h b/drivers/infiniband/hw/mthca/mthca_dev.h
index 4c1dcb4..f8160b8 100644
--- a/drivers/infiniband/hw/mthca/mthca_dev.h
+++ b/drivers/infiniband/hw/mthca/mthca_dev.h
@@ -496,7 +496,7 @@
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);
diff --git a/drivers/infiniband/hw/mthca/mthca_provider.h b/drivers/infiniband/hw/mthca/mthca_provider.h
index 6676a78..179a8f6 100644
--- a/drivers/infiniband/hw/mthca/mthca_provider.h
+++ b/drivers/infiniband/hw/mthca/mthca_provider.h
@@ -139,11 +139,12 @@
* a qp may be locked, with the send cq locked first. No other
* nesting should be done.
*
- * Each struct mthca_cq/qp also has an atomic_t ref count. The
- * pointer from the cq/qp_table to the struct counts as one reference.
- * This reference also is good for access through the consumer API, so
- * modifying the CQ/QP etc doesn't need to take another reference.
- * Access because of a completion being polled does need a reference.
+ * Each struct mthca_cq/qp also has an ref count, protected by the
+ * corresponding table lock. The pointer from the cq/qp_table to the
+ * struct counts as one reference. This reference also is good for
+ * access through the consumer API, so modifying the CQ/QP etc doesn't
+ * need to take another reference. Access to a QP because of a
+ * completion being polled does not need a reference either.
*
* Finally, each struct mthca_cq/qp has a wait_queue_head_t for the
* destroy function to sleep on.
@@ -159,8 +160,9 @@
* - decrement ref count; if zero, wake up waiters
*
* To destroy a CQ/QP, we can do the following:
- * - lock cq/qp_table, remove pointer, unlock cq/qp_table lock
- * - decrement ref count
+ * - lock cq/qp_table
+ * - remove pointer and decrement ref count
+ * - unlock cq/qp_table lock
* - wait_event until ref count is zero
*
* It is the consumer's responsibilty to make sure that no QP
@@ -197,7 +199,7 @@
struct mthca_cq {
struct ib_cq ibcq;
spinlock_t lock;
- atomic_t refcount;
+ int refcount;
int cqn;
u32 cons_index;
struct mthca_cq_buf buf;
@@ -217,7 +219,7 @@
struct mthca_srq {
struct ib_srq ibsrq;
spinlock_t lock;
- atomic_t refcount;
+ int refcount;
int srqn;
int max;
int max_gs;
@@ -254,7 +256,7 @@
struct mthca_qp {
struct ib_qp ibqp;
- atomic_t refcount;
+ int refcount;
u32 qpn;
int is_direct;
u8 port; /* for SQP and memfree use only */
diff --git a/drivers/infiniband/hw/mthca/mthca_qp.c b/drivers/infiniband/hw/mthca/mthca_qp.c
index f37b0e3..19765f6 100644
--- a/drivers/infiniband/hw/mthca/mthca_qp.c
+++ b/drivers/infiniband/hw/mthca/mthca_qp.c
@@ -240,7 +240,7 @@
spin_lock(&dev->qp_table.lock);
qp = mthca_array_get(&dev->qp_table.qp, qpn & (dev->limits.num_qps - 1));
if (qp)
- atomic_inc(&qp->refcount);
+ ++qp->refcount;
spin_unlock(&dev->qp_table.lock);
if (!qp) {
@@ -257,8 +257,10 @@
if (qp->ibqp.event_handler)
qp->ibqp.event_handler(&event, qp->ibqp.qp_context);
- if (atomic_dec_and_test(&qp->refcount))
+ spin_lock(&dev->qp_table.lock);
+ if (!--qp->refcount)
wake_up(&qp->wait);
+ spin_unlock(&dev->qp_table.lock);
}
static int to_mthca_state(enum ib_qp_state ib_state)
@@ -833,10 +835,10 @@
* entries and reinitialize the QP.
*/
if (new_state == IB_QPS_RESET && !qp->ibqp.uobject) {
- mthca_cq_clean(dev, to_mcq(qp->ibqp.send_cq)->cqn, qp->qpn,
+ mthca_cq_clean(dev, to_mcq(qp->ibqp.send_cq), qp->qpn,
qp->ibqp.srq ? to_msrq(qp->ibqp.srq) : NULL);
if (qp->ibqp.send_cq != qp->ibqp.recv_cq)
- mthca_cq_clean(dev, to_mcq(qp->ibqp.recv_cq)->cqn, qp->qpn,
+ mthca_cq_clean(dev, to_mcq(qp->ibqp.recv_cq), qp->qpn,
qp->ibqp.srq ? to_msrq(qp->ibqp.srq) : NULL);
mthca_wq_init(&qp->sq);
@@ -1096,7 +1098,7 @@
int ret;
int i;
- atomic_set(&qp->refcount, 1);
+ qp->refcount = 1;
init_waitqueue_head(&qp->wait);
qp->state = IB_QPS_RESET;
qp->atomic_rd_en = 0;
@@ -1318,6 +1320,17 @@
return err;
}
+static inline int get_qp_refcount(struct mthca_dev *dev, struct mthca_qp *qp)
+{
+ int c;
+
+ spin_lock_irq(&dev->qp_table.lock);
+ c = qp->refcount;
+ spin_unlock_irq(&dev->qp_table.lock);
+
+ return c;
+}
+
void mthca_free_qp(struct mthca_dev *dev,
struct mthca_qp *qp)
{
@@ -1339,14 +1352,14 @@
spin_lock(&dev->qp_table.lock);
mthca_array_clear(&dev->qp_table.qp,
qp->qpn & (dev->limits.num_qps - 1));
+ --qp->refcount;
spin_unlock(&dev->qp_table.lock);
if (send_cq != recv_cq)
spin_unlock(&recv_cq->lock);
spin_unlock_irq(&send_cq->lock);
- atomic_dec(&qp->refcount);
- wait_event(qp->wait, !atomic_read(&qp->refcount));
+ wait_event(qp->wait, !get_qp_refcount(dev, qp));
if (qp->state != IB_QPS_RESET)
mthca_MODIFY_QP(dev, qp->state, IB_QPS_RESET, qp->qpn, 0,
@@ -1358,10 +1371,10 @@
* unref the mem-free tables and free the QPN in our table.
*/
if (!qp->ibqp.uobject) {
- mthca_cq_clean(dev, to_mcq(qp->ibqp.send_cq)->cqn, qp->qpn,
+ mthca_cq_clean(dev, to_mcq(qp->ibqp.send_cq), qp->qpn,
qp->ibqp.srq ? to_msrq(qp->ibqp.srq) : NULL);
if (qp->ibqp.send_cq != qp->ibqp.recv_cq)
- mthca_cq_clean(dev, to_mcq(qp->ibqp.recv_cq)->cqn, qp->qpn,
+ mthca_cq_clean(dev, to_mcq(qp->ibqp.recv_cq), qp->qpn,
qp->ibqp.srq ? to_msrq(qp->ibqp.srq) : NULL);
mthca_free_memfree(dev, qp);
diff --git a/drivers/infiniband/hw/mthca/mthca_srq.c b/drivers/infiniband/hw/mthca/mthca_srq.c
index adcaf85..1ea4332 100644
--- a/drivers/infiniband/hw/mthca/mthca_srq.c
+++ b/drivers/infiniband/hw/mthca/mthca_srq.c
@@ -241,7 +241,7 @@
goto err_out_mailbox;
spin_lock_init(&srq->lock);
- atomic_set(&srq->refcount, 1);
+ srq->refcount = 1;
init_waitqueue_head(&srq->wait);
if (mthca_is_memfree(dev))
@@ -308,6 +308,17 @@
return err;
}
+static inline int get_srq_refcount(struct mthca_dev *dev, struct mthca_srq *srq)
+{
+ int c;
+
+ spin_lock_irq(&dev->srq_table.lock);
+ c = srq->refcount;
+ spin_unlock_irq(&dev->srq_table.lock);
+
+ return c;
+}
+
void mthca_free_srq(struct mthca_dev *dev, struct mthca_srq *srq)
{
struct mthca_mailbox *mailbox;
@@ -329,10 +340,10 @@
spin_lock_irq(&dev->srq_table.lock);
mthca_array_clear(&dev->srq_table.srq,
srq->srqn & (dev->limits.num_srqs - 1));
+ --srq->refcount;
spin_unlock_irq(&dev->srq_table.lock);
- atomic_dec(&srq->refcount);
- wait_event(srq->wait, !atomic_read(&srq->refcount));
+ wait_event(srq->wait, !get_srq_refcount(dev, srq));
if (!srq->ibsrq.uobject) {
mthca_free_srq_buf(dev, srq);
@@ -414,7 +425,7 @@
spin_lock(&dev->srq_table.lock);
srq = mthca_array_get(&dev->srq_table.srq, srqn & (dev->limits.num_srqs - 1));
if (srq)
- atomic_inc(&srq->refcount);
+ ++srq->refcount;
spin_unlock(&dev->srq_table.lock);
if (!srq) {
@@ -431,8 +442,10 @@
srq->ibsrq.event_handler(&event, srq->ibsrq.srq_context);
out:
- if (atomic_dec_and_test(&srq->refcount))
+ spin_lock(&dev->srq_table.lock);
+ if (!--srq->refcount)
wake_up(&srq->wait);
+ spin_unlock(&dev->srq_table.lock);
}
/*
