cuse: do not register multiple devices with identical names

Sysfs doesn't allow two devices with the same name, but we register a
sysfs entry for each cuse device without checking for name collisions.
This extends the registration to first check whether the name was already
registered.

To avoid race-conditions between the name-check and linking the device, we
need to protect the whole registration with a mutex.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 15 insertions, 6 deletions

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 048e89f25082..2a2797e2abc5 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -304,14 +304,14 @@ static void cuse_gendev_release(struct device *dev)
  */
 static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 {
-        struct cuse_conn *cc = fc_to_cc(fc);
+        struct cuse_conn *cc = fc_to_cc(fc), *pos;
         struct cuse_init_out *arg = req->out.args[0].value;
         struct page *page = req->pages[0];
         struct cuse_devinfo devinfo = { };
         struct device *dev;
         struct cdev *cdev;
         dev_t devt;
-        int rc;
+        int rc, i;
 
         if (req->out.h.error ||
             arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
@@ -355,15 +355,24 @@ static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
         dev_set_drvdata(dev, cc);
         dev_set_name(dev, "%s", devinfo.name);
 
+        mutex_lock(&cuse_lock);
+
+        /* make sure the device-name is unique */
+        for (i = 0; i < CUSE_CONNTBL_LEN; ++i) {
+                list_for_each_entry(pos, &cuse_conntbl[i], list)
+                        if (!strcmp(dev_name(pos->dev), dev_name(dev)))
+                                goto err_unlock;
+        }
+
         rc = device_add(dev);
         if (rc)
-                goto err_device;
+                goto err_unlock;
 
         /* register cdev */
         rc = -ENOMEM;
         cdev = cdev_alloc();
         if (!cdev)
-                goto err_device;
+                goto err_unlock;
 
         cdev->owner = THIS_MODULE;
         cdev->ops = &cuse_frontend_fops;
@@ -376,7 +385,6 @@ static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
         cc->cdev = cdev;
 
         /* make the device available */
-        mutex_lock(&cuse_lock);
         list_add(&cc->list, cuse_conntbl_head(devt));
         mutex_unlock(&cuse_lock);
 
@@ -390,7 +398,8 @@ out:
 
 err_cdev:
         cdev_del(cdev);
-err_device:
+err_unlock:
+        mutex_unlock(&cuse_lock);
         put_device(dev);
 err_region:
         unregister_chrdev_region(devt, 1);