firewire: cdev: use an idr rather than a linked list for resources

The current code uses a linked list and a counter for storing
resources and the corresponding handle numbers.  By changing to an idr
we can be safe from counter wrap-around giving two resources the same
handle.

Furthermore, the deallocation ioctls now check whether the resource to
be freed is of the intended type.

Signed-off-by: Jay Fenlason <fenlason@redhat.com>

Some rework by Stefan R:
  - The idr API documentation says we get an ID within 0...0x7fffffff.
    Hence we can rest assured that idr handles fit into cdev handles.
  - Fix some races.  Add a client->in_shutdown flag for this purpose.
  - Add allocation retry to add_client_resource().
  - It is possible to use idr_for_each() in fw_device_op_release().
  - Fix ioctl_send_response() regression.
  - Small style changes.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 114 insertions, 51 deletions

diff --git a/drivers/firewire/fw-cdev.c b/drivers/firewire/fw-cdev.c
index 4dd66c1a36da..094aee5c8bcf 100644
--- a/drivers/firewire/fw-cdev.c
+++ b/drivers/firewire/fw-cdev.c
@@ -41,10 +41,12 @@
 #include "fw-device.h"
 
 struct client;
+struct client_resource;
+typedef void (*client_resource_release_fn_t)(struct client *,
+                                             struct client_resource *);
 struct client_resource {
-        struct list_head link;
-        void (*release)(struct client *client, struct client_resource *r);
-        u32 handle;
+        client_resource_release_fn_t release;
+        int handle;
 };
 
 /*
@@ -78,9 +80,10 @@ struct iso_interrupt {
 struct client {
         u32 version;
         struct fw_device *device;
+
         spinlock_t lock;
-        u32 resource_handle;
-        struct list_head resource_list;
+        bool in_shutdown;
+        struct idr resource_idr;
         struct list_head event_list;
         wait_queue_head_t wait;
         u64 bus_reset_closure;
@@ -126,9 +129,9 @@ static int fw_device_op_open(struct inode *inode, struct file *file)
         }
 
         client->device = device;
-        INIT_LIST_HEAD(&client->event_list);
-        INIT_LIST_HEAD(&client->resource_list);
         spin_lock_init(&client->lock);
+        idr_init(&client->resource_idr);
+        INIT_LIST_HEAD(&client->event_list);
         init_waitqueue_head(&client->wait);
 
         file->private_data = client;
@@ -151,7 +154,10 @@ static void queue_event(struct client *client, struct event *event,
         event->v[1].size = size1;
 
         spin_lock_irqsave(&client->lock, flags);
-        list_add_tail(&event->link, &client->event_list);
+        if (client->in_shutdown)
+                kfree(event);
+        else
+                list_add_tail(&event->link, &client->event_list);
         spin_unlock_irqrestore(&client->lock, flags);
 
         wake_up_interruptible(&client->wait);
@@ -310,34 +316,49 @@ static int ioctl_get_info(struct client *client, void *buffer)
         return 0;
 }
 
-static void
-add_client_resource(struct client *client, struct client_resource *resource)
+static int
+add_client_resource(struct client *client, struct client_resource *resource,
+                    gfp_t gfp_mask)
 {
         unsigned long flags;
+        int ret;
+
+ retry:
+        if (idr_pre_get(&client->resource_idr, gfp_mask) == 0)
+                return -ENOMEM;
 
         spin_lock_irqsave(&client->lock, flags);
-        list_add_tail(&resource->link, &client->resource_list);
-        resource->handle = client->resource_handle++;
+        if (client->in_shutdown)
+                ret = -ECANCELED;
+        else
+                ret = idr_get_new(&client->resource_idr, resource,
+                                  &resource->handle);
         spin_unlock_irqrestore(&client->lock, flags);
+
+        if (ret == -EAGAIN)
+                goto retry;
+
+        return ret < 0 ? ret : 0;
 }
 
 static int
 release_client_resource(struct client *client, u32 handle,
+                        client_resource_release_fn_t release,
                         struct client_resource **resource)
 {
         struct client_resource *r;
         unsigned long flags;
 
         spin_lock_irqsave(&client->lock, flags);
-        list_for_each_entry(r, &client->resource_list, link) {
-                if (r->handle == handle) {
-                        list_del(&r->link);
-                        break;
-                }
-        }
+        if (client->in_shutdown)
+                r = NULL;
+        else
+                r = idr_find(&client->resource_idr, handle);
+        if (r && r->release == release)
+                idr_remove(&client->resource_idr, handle);
         spin_unlock_irqrestore(&client->lock, flags);
 
-        if (&r->link == &client->resource_list)
+        if (!(r && r->release == release))
                 return -EINVAL;
 
         if (resource)
@@ -372,7 +393,12 @@ complete_transaction(struct fw_card *card, int rcode,
                 memcpy(r->data, payload, r->length);
 
         spin_lock_irqsave(&client->lock, flags);
-        list_del(&response->resource.link);
+        /*
+         * If called while in shutdown, the idr tree must be left untouched.
+         * The idr handle will be removed later.
+         */
+        if (!client->in_shutdown)
+                idr_remove(&client->resource_idr, response->resource.handle);
         spin_unlock_irqrestore(&client->lock, flags);
 
         r->type   = FW_CDEV_EVENT_RESPONSE;
@@ -416,7 +442,7 @@ static int ioctl_send_request(struct client *client, void *buffer)
             copy_from_user(response->response.data,
                            u64_to_uptr(request->data), request->length)) {
                 ret = -EFAULT;
-                goto err;
+                goto failed;
         }
 
         switch (request->tcode) {
@@ -434,11 +460,13 @@ static int ioctl_send_request(struct client *client, void *buffer)
                 break;
         default:
                 ret = -EINVAL;
-                goto err;
+                goto failed;
         }
 
         response->resource.release = release_transaction;
-        add_client_resource(client, &response->resource);
+        ret = add_client_resource(client, &response->resource, GFP_KERNEL);
+        if (ret < 0)
+                goto failed;
 
         fw_send_request(device->card, &response->transaction,
                         request->tcode & 0x1f,
@@ -453,7 +481,7 @@ static int ioctl_send_request(struct client *client, void *buffer)
                 return sizeof(request) + request->length;
         else
                 return sizeof(request);
- err:
+ failed:
         kfree(response);
 
         return ret;
@@ -500,22 +528,21 @@ handle_request(struct fw_card *card, struct fw_request *r,
         struct request *request;
         struct request_event *e;
         struct client *client = handler->client;
+        int ret;
 
         request = kmalloc(sizeof(*request), GFP_ATOMIC);
         e = kmalloc(sizeof(*e), GFP_ATOMIC);
-        if (request == NULL || e == NULL) {
-                kfree(request);
-                kfree(e);
-                fw_send_response(card, r, RCODE_CONFLICT_ERROR);
-                return;
-        }
+        if (request == NULL || e == NULL)
+                goto failed;
 
         request->request = r;
         request->data    = payload;
         request->length  = length;
 
         request->resource.release = release_request;
-        add_client_resource(client, &request->resource);
+        ret = add_client_resource(client, &request->resource, GFP_ATOMIC);
+        if (ret < 0)
+                goto failed;
 
         e->request.type    = FW_CDEV_EVENT_REQUEST;
         e->request.tcode   = tcode;
@@ -526,6 +553,12 @@ handle_request(struct fw_card *card, struct fw_request *r,
 
         queue_event(client, &e->event,
                     &e->request, sizeof(e->request), payload, length);
+        return;
+
+ failed:
+        kfree(request);
+        kfree(e);
+        fw_send_response(card, r, RCODE_CONFLICT_ERROR);
 }
 
 static void
@@ -544,6 +577,7 @@ static int ioctl_allocate(struct client *client, void *buffer)
         struct fw_cdev_allocate *request = buffer;
         struct address_handler *handler;
         struct fw_address_region region;
+        int ret;
 
         handler = kmalloc(sizeof(*handler), GFP_KERNEL);
         if (handler == NULL)
@@ -563,7 +597,11 @@ static int ioctl_allocate(struct client *client, void *buffer)
         }
 
         handler->resource.release = release_address_handler;
-        add_client_resource(client, &handler->resource);
+        ret = add_client_resource(client, &handler->resource, GFP_KERNEL);
+        if (ret < 0) {
+                release_address_handler(client, &handler->resource);
+                return ret;
+        }
         request->handle = handler->resource.handle;
 
         return 0;
@@ -573,7 +611,8 @@ static int ioctl_deallocate(struct client *client, void *buffer)
 {
         struct fw_cdev_deallocate *request = buffer;
 
-        return release_client_resource(client, request->handle, NULL);
+        return release_client_resource(client, request->handle,
+                                       release_address_handler, NULL);
 }
 
 static int ioctl_send_response(struct client *client, void *buffer)
@@ -582,8 +621,10 @@ static int ioctl_send_response(struct client *client, void *buffer)
         struct client_resource *resource;
         struct request *r;
 
-        if (release_client_resource(client, request->handle, &resource) < 0)
+        if (release_client_resource(client, request->handle,
+                                    release_request, &resource) < 0)
                 return -EINVAL;
+
         r = container_of(resource, struct request, resource);
         if (request->length < r->length)
                 r->length = request->length;
@@ -626,7 +667,7 @@ static int ioctl_add_descriptor(struct client *client, void *buffer)
 {
         struct fw_cdev_add_descriptor *request = buffer;
         struct descriptor *descriptor;
-        int retval;
+        int ret;
 
         if (request->length > 256)
                 return -EINVAL;
@@ -638,8 +679,8 @@ static int ioctl_add_descriptor(struct client *client, void *buffer)
 
         if (copy_from_user(descriptor->data,
                            u64_to_uptr(request->data), request->length * 4)) {
-                kfree(descriptor);
-                return -EFAULT;
+                ret = -EFAULT;
+                goto failed;
         }
 
         descriptor->d.length = request->length;
@@ -647,24 +688,31 @@ static int ioctl_add_descriptor(struct client *client, void *buffer)
         descriptor->d.key = request->key;
         descriptor->d.data = descriptor->data;
 
-        retval = fw_core_add_descriptor(&descriptor->d);
-        if (retval < 0) {
-                kfree(descriptor);
-                return retval;
-        }
+        ret = fw_core_add_descriptor(&descriptor->d);
+        if (ret < 0)
+                goto failed;
 
         descriptor->resource.release = release_descriptor;
-        add_client_resource(client, &descriptor->resource);
+        ret = add_client_resource(client, &descriptor->resource, GFP_KERNEL);
+        if (ret < 0) {
+                fw_core_remove_descriptor(&descriptor->d);
+                goto failed;
+        }
         request->handle = descriptor->resource.handle;
 
         return 0;
+ failed:
+        kfree(descriptor);
+
+        return ret;
 }
 
 static int ioctl_remove_descriptor(struct client *client, void *buffer)
 {
         struct fw_cdev_remove_descriptor *request = buffer;
 
-        return release_client_resource(client, request->handle, NULL);
+        return release_client_resource(client, request->handle,
+                                       release_descriptor, NULL);
 }
 
 static void
@@ -1003,11 +1051,21 @@ static int fw_device_op_mmap(struct file *file, struct vm_area_struct *vma)
         return retval;
 }
 
+static int shutdown_resource(int id, void *p, void *data)
+{
+        struct client_resource *r = p;
+        struct client *client = data;
+
+        r->release(client, r);
+
+        return 0;
+}
+
 static int fw_device_op_release(struct inode *inode, struct file *file)
 {
         struct client *client = file->private_data;
         struct event *e, *next_e;
-        struct client_resource *r, *next_r;
+        unsigned long flags;
 
         mutex_lock(&client->device->client_list_mutex);
         list_del(&client->link);
@@ -1019,17 +1077,22 @@ static int fw_device_op_release(struct inode *inode, struct file *file)
         if (client->iso_context)
                 fw_iso_context_destroy(client->iso_context);
 
-        list_for_each_entry_safe(r, next_r, &client->resource_list, link)
-                r->release(client, r);
+        /* Freeze client->resource_idr and client->event_list */
+        spin_lock_irqsave(&client->lock, flags);
+        client->in_shutdown = true;
+        spin_unlock_irqrestore(&client->lock, flags);
 
-        /*
-         * FIXME: We should wait for the async tasklets to stop
-         * running before freeing the memory.
-         */
+        idr_for_each(&client->resource_idr, shutdown_resource, client);
+        idr_remove_all(&client->resource_idr);
+        idr_destroy(&client->resource_idr);
 
         list_for_each_entry_safe(e, next_e, &client->event_list, link)
                 kfree(e);
 
+        /*
+         * FIXME: client should be reference-counted.  It's extremely unlikely
+         * but there may still be transactions being completed at this point.
+         */
         fw_device_put(client->device);
         kfree(client);