ieee1394: raw1394: prevent unloading of low-level driver

Unloading the low-level driver module of a FireWire host can lead to
all sorts of trouble if a raw1394 userspace client is using the host.
Just disallow it by incrementing the LLD's module reference count on
a RAW1394_REQ_SET_CARD write operation.  Decrement it when the file
is closed.

This feature wouldn't be relevant if "modprobe -r video1394" or
"modprobe -r dv1394" didn't automatically unload ohci1394 too.
http://bugzilla.kernel.org/show_bug.cgi?id=7701

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Dan Dennedy <dan@dennedy.org>

1 files changed, 29 insertions, 19 deletions

diff --git a/drivers/ieee1394/raw1394.c b/drivers/ieee1394/raw1394.c
index ad2108f27a0..a77a832828c 100644
--- a/drivers/ieee1394/raw1394.c
+++ b/drivers/ieee1394/raw1394.c
@@ -636,27 +636,32 @@ static int state_initialized(struct file_info *fi, struct pending_request *req)
 
         case RAW1394_REQ_SET_CARD:
                 spin_lock_irqsave(&host_info_lock, flags);
-                if (req->req.misc < host_count) {
-                        list_for_each_entry(hi, &host_info_list, list) {
-                                if (!req->req.misc--)
-                                        break;
-                        }
-                        get_device(&hi->host->device);  // XXX Need to handle failure case
-                        list_add_tail(&fi->list, &hi->file_info_list);
-                        fi->host = hi->host;
-                        fi->state = connected;
-
-                        req->req.error = RAW1394_ERROR_NONE;
-                        req->req.generation = get_hpsb_generation(fi->host);
-                        req->req.misc = (fi->host->node_id << 16)
-                            | fi->host->node_count;
-                        if (fi->protocol_version > 3) {
-                                req->req.misc |=
-                                    NODEID_TO_NODE(fi->host->irm_id) << 8;
-                        }
-                } else {
+                if (req->req.misc >= host_count) {
                         req->req.error = RAW1394_ERROR_INVALID_ARG;
+                        goto out_set_card;
                 }
+                list_for_each_entry(hi, &host_info_list, list)
+                        if (!req->req.misc--)
+                                break;
+                get_device(&hi->host->device); /* FIXME handle failure case */
+                list_add_tail(&fi->list, &hi->file_info_list);
+
+                /* prevent unloading of the host's low-level driver */
+                if (!try_module_get(hi->host->driver->owner)) {
+                        req->req.error = RAW1394_ERROR_ABORTED;
+                        goto out_set_card;
+                }
+                WARN_ON(fi->host);
+                fi->host = hi->host;
+                fi->state = connected;
+
+                req->req.error = RAW1394_ERROR_NONE;
+                req->req.generation = get_hpsb_generation(fi->host);
+                req->req.misc = (fi->host->node_id << 16)
+                                | fi->host->node_count;
+                if (fi->protocol_version > 3)
+                        req->req.misc |= NODEID_TO_NODE(fi->host->irm_id) << 8;
+out_set_card:
                 spin_unlock_irqrestore(&host_info_lock, flags);
 
                 req->req.length = 0;
@@ -2955,6 +2960,11 @@ static int raw1394_release(struct inode *inode, struct file *file)
                 put_device(&fi->host->device);
         }
 
+        spin_lock_irqsave(&host_info_lock, flags);
+        if (fi->host)
+                module_put(fi->host->driver->owner);
+        spin_unlock_irqrestore(&host_info_lock, flags);
+
         kfree(fi);
 
         return 0;