s390/qeth: serialize cmd reply with concurrent timeout

Callbacks for a cmd reply run outside the protection of card->lock, to
allow for additional cmds to be issued & enqueued in parallel.

When qeth_send_control_data() bails out for a cmd without having
received a reply (eg. due to timeout), its callback may concurrently be
processing a reply that just arrived. In this case, the callback
potentially accesses a stale reply->reply_param area that eg. was
on-stack and has already been released.

To avoid this race, add some locking so that qeth_send_control_data()
can (1) wait for a concurrently running callback, and (2) zap any
pending callback that still wants to run.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index c7ee07ce3615d93a9d02b5a507ca0ef008a9698f..28db887d38edc809669b32fb146fcd8d64185f92 100644 (file)
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -629,6 +629,7 @@ struct qeth_seqno {
 struct qeth_reply {
        struct list_head list;
        struct completion received;
+       spinlock_t lock;
        int (*callback)(struct qeth_card *, struct qeth_reply *,
                unsigned long);
        u32 seqno;

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 4d0caeebc80210d3a130a2ec19574e0e1824b1bb..9c3310c4d61d670426bfa5a842b5f2c750119f04 100644 (file)
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -544,6 +544,7 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card *card)
        if (reply) {
                refcount_set(&reply->refcnt, 1);
                init_completion(&reply->received);
+               spin_lock_init(&reply->lock);
        }
        return reply;
 }
@@ -799,6 +800,13 @@ static void qeth_issue_next_read_cb(struct qeth_card *card,
 
        if (!reply->callback) {
                rc = 0;
+               goto no_callback;
+       }
+
+       spin_lock_irqsave(&reply->lock, flags);
+       if (reply->rc) {
+               /* Bail out when the requestor has already left: */
+               rc = reply->rc;
        } else {
                if (cmd) {
                        reply->offset = (u16)((char *)cmd - (char *)iob->data);
@@ -807,7 +815,9 @@ static void qeth_issue_next_read_cb(struct qeth_card *card,
                        rc = reply->callback(card, reply, (unsigned long)iob);
                }
        }
+       spin_unlock_irqrestore(&reply->lock, flags);
 
+no_callback:
        if (rc <= 0)
                qeth_notify_reply(reply, rc);
        qeth_put_reply(reply);
@@ -1749,6 +1759,16 @@ static int qeth_send_control_data(struct qeth_card *card,
                rc = (timeout == -ERESTARTSYS) ? -EINTR : -ETIME;
 
        qeth_dequeue_reply(card, reply);
+
+       if (reply_cb) {
+               /* Wait until the callback for a late reply has completed: */
+               spin_lock_irq(&reply->lock);
+               if (rc)
+                       /* Zap any callback that's still pending: */
+                       reply->rc = rc;
+               spin_unlock_irq(&reply->lock);
+       }
+
        if (!rc)
                rc = reply->rc;
        qeth_put_reply(reply);