[v3 PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op(): Uninitialized variables" warning.

[Aiswarya Cyriac]

This commit fixes the following warning when building virtio_snd driver.

"
*** CID 1583619:  Uninitialized variables  (UNINIT)
sound/virtio/virtio_kctl.c:294 in virtsnd_kctl_tlv_op()
288
289                     break;
290             }
291
292             kfree(tlv);
293
vvv     CID 1583619:  Uninitialized variables  (UNINIT)
vvv     Using uninitialized value "rc".
294             return rc;
295     }
296
297     /**
298      * virtsnd_kctl_get_enum_items() - Query items for the ENUMERATED 
element type.
299      * @snd: VirtIO sound device.
"

This warning is caused by the absence of the "default" branch in the
switch-block, and is a false positive because the kernel calls
virtsnd_kctl_tlv_op() only with values for op_flag processed in
this block.

Also, this commit unifies the cleanup path for all possible control
paths in the callback function.

Signed-off-by: Anton Yakovlev <anton.yakov...@opensynergy.com>
Signed-off-by: Aiswarya Cyriac <aiswarya.cyr...@opensynergy.com>
Reported-by: coverity-bot <keescook+coverity-...@chromium.org>
Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
---
 sound/virtio/virtio_kctl.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/sound/virtio/virtio_kctl.c b/sound/virtio/virtio_kctl.c
index 0c6ac74aca1e..40606eb381af 100644
--- a/sound/virtio/virtio_kctl.c
+++ b/sound/virtio/virtio_kctl.c
@@ -253,8 +253,8 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol 
*kcontrol, int op_flag,
 
        tlv = kzalloc(size, GFP_KERNEL);
        if (!tlv) {
-               virtsnd_ctl_msg_unref(msg);
-               return -ENOMEM;
+               rc = -ENOMEM;
+               goto on_cleanup;
        }
 
        sg_init_one(&sg, tlv, size);
@@ -266,6 +266,11 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol 
*kcontrol, int op_flag,
        case SNDRV_CTL_TLV_OP_READ:
                hdr->hdr.code = cpu_to_le32(VIRTIO_SND_R_CTL_TLV_READ);
 
+               /* Since virtsnd_ctl_msg_send() drops the reference, we increase
+                * the counter to be consistent with the on_cleanup path.
+                */
+               virtsnd_ctl_msg_ref(msg);
+
                rc = virtsnd_ctl_msg_send(snd, msg, NULL, &sg, false);
                if (!rc) {
                        if (copy_to_user(utlv, tlv, size))
@@ -281,14 +286,26 @@ static int virtsnd_kctl_tlv_op(struct snd_kcontrol 
*kcontrol, int op_flag,
                        hdr->hdr.code =
                                cpu_to_le32(VIRTIO_SND_R_CTL_TLV_COMMAND);
 
-               if (copy_from_user(tlv, utlv, size))
+               if (copy_from_user(tlv, utlv, size)) {
                        rc = -EFAULT;
-               else
+               } else {
+                       /* Same as the comment above */
+                       virtsnd_ctl_msg_ref(msg);
+
                        rc = virtsnd_ctl_msg_send(snd, msg, &sg, NULL, false);
+               }
+
+               break;
+       default:
+               rc = -EINVAL;
+               WARN_ON(1);
 
                break;
        }
 
+on_cleanup:
+       virtsnd_ctl_msg_unref(msg);
+
        kfree(tlv);
 
        return rc;
-- 
2.43.0