s390/qeth: don't clobber buffer on async TX completion

If qeth_qdio_output_handler() detects that a transmit requires async
completion, it replaces the pending buffer's metadata object
(qeth_qdio_out_buffer) so that this queue buffer can be re-used while
the data is pending completion.

Later when the CQ indicates async completion of such a metadata object,
qeth_qdio_cq_handler() tries to free any data associated with this
object (since HW has now completed the transfer). By calling
qeth_clear_output_buffer(), it erronously operates on the queue buffer
that _previously_ belonged to this transfer ... but which has been
potentially re-used several times by now.
This results in double-free's of the buffer's data, and failing
transmits as the buffer descriptor is scrubbed in mid-air.

The correct way of handling this situation is to
1. scrub the queue buffer when it is prepared for re-use, and
2. later obtain the data addresses from the async-completion notifier
   (ie. the AOB), instead of the queue buffer.

All this only affects qeth devices used for af_iucv HiperTransport.

Fixes: 0da9581ddb0f ("qeth: exploit asynchronous delivery of storage blocks")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index 2a5fec55bf60f6f30fd684e1c8c5c9a594aa8e75..940fd7b558d329a35d88c87831762ac3d6cd2117 100644 (file)
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -829,6 +829,17 @@ struct qeth_trap_id {
 /*some helper functions*/
 #define QETH_CARD_IFNAME(card) (((card)->dev)? (card)->dev->name : "")
 
+static inline void qeth_scrub_qdio_buffer(struct qdio_buffer *buf,
+                                         unsigned int elements)
+{
+       unsigned int i;
+
+       for (i = 0; i < elements; i++)
+               memset(&buf->element[i], 0, sizeof(struct qdio_buffer_element));
+       buf->element[14].sflags = 0;
+       buf->element[15].sflags = 0;
+}
+
 /**
  * qeth_get_elements_for_range() -     find number of SBALEs to cover range.
  * @start:                             Start of the address range.

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 9d9182ed8ac458fe6d687843051b8e16d9e7618d..d20a69a3bc40710c59738b3e99c98f7e09df3996 100644 (file)
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -73,9 +73,6 @@ static void qeth_notify_skbs(struct qeth_qdio_out_q *queue,
                struct qeth_qdio_out_buffer *buf,
                enum iucv_tx_notify notification);
 static void qeth_release_skbs(struct qeth_qdio_out_buffer *buf);
-static void qeth_clear_output_buffer(struct qeth_qdio_out_q *queue,
-               struct qeth_qdio_out_buffer *buf,
-               enum qeth_qdio_buffer_states newbufstate);
 static int qeth_init_qdio_out_buf(struct qeth_qdio_out_q *, int);
 
 struct workqueue_struct *qeth_wq;
@@ -489,6 +486,7 @@ static void qeth_qdio_handle_aob(struct qeth_card *card,
        struct qaob *aob;
        struct qeth_qdio_out_buffer *buffer;
        enum iucv_tx_notify notification;
+       unsigned int i;
 
        aob = (struct qaob *) phys_to_virt(phys_aob_addr);
        QETH_CARD_TEXT(card, 5, "haob");
@@ -513,10 +511,18 @@ static void qeth_qdio_handle_aob(struct qeth_card *card,
        qeth_notify_skbs(buffer->q, buffer, notification);
 
        buffer->aob = NULL;
-       qeth_clear_output_buffer(buffer->q, buffer,
-                                QETH_QDIO_BUF_HANDLED_DELAYED);
+       /* Free dangling allocations. The attached skbs are handled by
+        * qeth_cleanup_handled_pending().
+        */
+       for (i = 0;
+            i < aob->sb_count && i < QETH_MAX_BUFFER_ELEMENTS(card);
+            i++) {
+               if (aob->sba[i] && buffer->is_header[i])
+                       kmem_cache_free(qeth_core_header_cache,
+                                       (void *) aob->sba[i]);
+       }
+       atomic_set(&buffer->state, QETH_QDIO_BUF_HANDLED_DELAYED);
 
-       /* from here on: do not touch buffer anymore */
        qdio_release_aob(aob);
 }
 
@@ -3759,6 +3765,10 @@ static void qeth_qdio_output_handler(struct ccw_device *ccwdev,
                        QETH_CARD_TEXT(queue->card, 5, "aob");
                        QETH_CARD_TEXT_(queue->card, 5, "%lx",
                                        virt_to_phys(buffer->aob));
+
+                       /* prepare the queue slot for re-use: */
+                       qeth_scrub_qdio_buffer(buffer->buffer,
+                                              QETH_MAX_BUFFER_ELEMENTS(card));
                        if (qeth_init_qdio_out_buf(queue, bidx)) {
                                QETH_CARD_TEXT(card, 2, "outofbuf");
                                qeth_schedule_recovery(card);