hw/audio/virtio-sound: fix heap buffer overflow

Currently, the guest may write to the device configuration space,
whereas the virtio sound device specification in chapter 5.14.4
clearly states that the fields in the device configuration space
are driver-read-only.

Remove the set_config function from the virtio_snd class.

This also prevents a heap buffer overflow. See QEMU issue #2296.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2296
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20240901130112.8242-1-vr_qemu@t-online.de>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 7fc6611cad3e9627b23ce83e550b668abba6c886)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/audio/trace-events

@@ -41,7 +41,6 @@ asc_update_irq(int irq, int a, int b) "set IRQ to %d (A: 0x%x B: 0x%x)"
 
 #virtio-snd.c
 virtio_snd_get_config(void *vdev, uint32_t jacks, uint32_t streams, uint32_t chmaps) "snd %p: get_config jacks=%"PRIu32" streams=%"PRIu32" chmaps=%"PRIu32""
-virtio_snd_set_config(void *vdev, uint32_t jacks, uint32_t new_jacks, uint32_t streams, uint32_t new_streams, uint32_t chmaps, uint32_t new_chmaps) "snd %p: set_config jacks from %"PRIu32"->%"PRIu32", streams from %"PRIu32"->%"PRIu32", chmaps from %"PRIu32"->%"PRIu32
 virtio_snd_get_features(void *vdev, uint64_t features) "snd %p: get_features 0x%"PRIx64
 virtio_snd_vm_state_running(void) "vm state running"
 virtio_snd_vm_state_stopped(void) "vm state stopped"

hw/audio/virtio-snd.c

@@ -107,29 +107,6 @@ virtio_snd_get_config(VirtIODevice *vdev, uint8_t *config)
 
 }
 
-static void
-virtio_snd_set_config(VirtIODevice *vdev, const uint8_t *config)
-{
-    VirtIOSound *s = VIRTIO_SND(vdev);
-    const virtio_snd_config *sndconfig =
-        (const virtio_snd_config *)config;
-
-
-   trace_virtio_snd_set_config(vdev,
-                               s->snd_conf.jacks,
-                               sndconfig->jacks,
-                               s->snd_conf.streams,
-                               sndconfig->streams,
-                               s->snd_conf.chmaps,
-                               sndconfig->chmaps);
-
-    memcpy(&s->snd_conf, sndconfig, sizeof(virtio_snd_config));
-    le32_to_cpus(&s->snd_conf.jacks);
-    le32_to_cpus(&s->snd_conf.streams);
-    le32_to_cpus(&s->snd_conf.chmaps);
-
-}
-
 static void
 virtio_snd_pcm_buffer_free(VirtIOSoundPCMBuffer *buffer)
 {
@@ -1400,7 +1377,6 @@ static void virtio_snd_class_init(ObjectClass *klass, void *data)
     vdc->realize = virtio_snd_realize;
     vdc->unrealize = virtio_snd_unrealize;
     vdc->get_config = virtio_snd_get_config;
-    vdc->set_config = virtio_snd_set_config;
     vdc->get_features = get_features;
     vdc->reset = virtio_snd_reset;
     vdc->legacy_features = 0;