firewire: net: fix use after free

Commit 8408dc1c14 "firewire: net: use dev_printk API" introduced a
use-after-free in a failure path.  fwnet_transmit_packet_failed(ptask)
may free ptask, then the dev_err() call dereferenced it.  The fix is
straightforward; simply reorder the two calls.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org # v3.4+
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/net.c

@@ -929,8 +929,6 @@ static void fwnet_write_complete(struct fw_card *card, int rcode,
 	if (rcode == RCODE_COMPLETE) {
 		fwnet_transmit_packet_done(ptask);
 	} else {
-		fwnet_transmit_packet_failed(ptask);
-
 		if (printk_timed_ratelimit(&j,  1000) || rcode != last_rcode) {
 			dev_err(&ptask->dev->netdev->dev,
 				"fwnet_write_complete failed: %x (skipped %d)\n",
@@ -938,9 +936,11 @@ static void fwnet_write_complete(struct fw_card *card, int rcode,
 
 			errors_skipped = 0;
 			last_rcode = rcode;
-		} else
+		} else {
 			errors_skipped++;
 		}
+		fwnet_transmit_packet_failed(ptask);
+	}
 }
 
 static int fwnet_send_packet(struct fwnet_packet_task *ptask)