virtio-rng: fixes for device registration/unregistration

There are several fixes in this patch (mostly because it's hard
splitting them up):

 - Revert the name field in struct hwrng back to 'const'. Also, don't
do an extra kmalloc for the name - just wasteful.
 - Deal with allocation failures properly.
 - Use IDA to allocate device number instead of brute forcing one.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index 5b25daa7f798a1da01fd3bad3893275cb918c9a5..f3e71501de5409cb9947b851d2f689ab76545391 100644 (file)
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -25,6 +25,7 @@
 #include <linux/virtio_rng.h>
 #include <linux/module.h>
 
+static DEFINE_IDA(rng_index_ida);
 
 struct virtrng_info {
        struct virtio_device *vdev;
@@ -33,6 +34,8 @@ struct virtrng_info {
        unsigned int data_avail;
        struct completion have_data;
        bool busy;
+       char name[25];
+       int index;
 };
 
 static void random_recv_done(struct virtqueue *vq)
@@ -92,41 +95,45 @@ static void virtio_cleanup(struct hwrng *rng)
 
 static int probe_common(struct virtio_device *vdev)
 {
-       int err, i;
+       int err, index;
        struct virtrng_info *vi = NULL;
 
        vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
-       vi->hwrng.name = kmalloc(40, GFP_KERNEL);
+       if (!vi)
+               return -ENOMEM;
+
+       vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
+       if (index < 0) {
+               kfree(vi);
+               return index;
+       }
+       sprintf(vi->name, "virtio_rng.%d", index);
        init_completion(&vi->have_data);
 
-       vi->hwrng.read = virtio_read;
-       vi->hwrng.cleanup = virtio_cleanup;
-       vi->hwrng.priv = (unsigned long)vi;
+       vi->hwrng = (struct hwrng) {
+               .read = virtio_read,
+               .cleanup = virtio_cleanup,
+               .priv = (unsigned long)vi,
+               .name = vi->name,
+       };
        vdev->priv = vi;
 
        /* We expect a single virtqueue. */
        vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
        if (IS_ERR(vi->vq)) {
                err = PTR_ERR(vi->vq);
-               kfree(vi->hwrng.name);
                vi->vq = NULL;
                kfree(vi);
-               vi = NULL;
+               ida_simple_remove(&rng_index_ida, index);
                return err;
        }
 
-       i = 0;
-       do {
-               sprintf(vi->hwrng.name, "virtio_rng.%d", i++);
-               err = hwrng_register(&vi->hwrng);
-       } while (err == -EEXIST);
-
+       err = hwrng_register(&vi->hwrng);
        if (err) {
                vdev->config->del_vqs(vdev);
-               kfree(vi->hwrng.name);
                vi->vq = NULL;
                kfree(vi);
-               vi = NULL;
+               ida_simple_remove(&rng_index_ida, index);
                return err;
        }
 
@@ -140,10 +147,8 @@ static void remove_common(struct virtio_device *vdev)
        vi->busy = false;
        hwrng_unregister(&vi->hwrng);
        vdev->config->del_vqs(vdev);
-       kfree(vi->hwrng.name);
-       vi->vq = NULL;
+       ida_simple_remove(&rng_index_ida, vi->index);
        kfree(vi);
-       vi = NULL;
 }
 
 static int virtrng_probe(struct virtio_device *vdev)

diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index 02d9c87be54c15341aa2c459294f964f85cb7b6e..b4b0eef5fddf381d9d842658a3adb29f17877883 100644 (file)
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -31,7 +31,7 @@
  * @priv:              Private data, for use by the RNG driver.
  */
 struct hwrng {
-       char *name;
+       const char *name;
        int (*init)(struct hwrng *rng);
        void (*cleanup)(struct hwrng *rng);
        int (*data_present)(struct hwrng *rng, int wait);