linux-kernel - [v2 PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv

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Message-Id: <20240214093813.578906-1-aiswarya.cyriac@opensynergy.com>
Date: Wed, 14 Feb 2024 10:38:13 +0100
From: Aiswarya Cyriac <aiswarya.cyriac@...nsynergy.com>
To: mst@...hat.com,
	jasowang@...hat.com,
	perex@...ex.cz,
	tiwai@...e.com,
	linux-kernel@...r.kernel.org,
	alsa-devel@...a-project.org,
	virtualization@...ts.linux-foundation.org,
	virtio-dev@...ts.oasis-open.org
Cc: Aiswarya Cyriac <aiswarya.cyriac@...nsynergy.com>,
	Anton Yakovlev <anton.yakovlev@...nsynergy.com>,
	coverity-bot <keescook+coverity-bot@...omium.org>
Subject: [v2 PATCH] ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op(): Uninitialized variables" warning.

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.yakovlev@...nsynergy.com>
Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@...nsynergy.com>
Reported-by: coverity-bot <keescook+coverity-bot@...omium.org>
Addresses-Coverity-ID: 1583619 ("Uninitialized variables")
Fixes: d6568e3de42d ("ALSA: virtio: add support for audio controls")
---
 sound/virtio/virtio_kctl.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/sound/virtio/virtio_kctl.c b/sound/virtio/virtio_kctl.c
index 0c6ac74aca1e..89e29a496dbe 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 +286,25 @@ 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;
 
 		break;
 	}
 
+on_cleanup:
+	virtsnd_ctl_msg_unref(msg);
+
 	kfree(tlv);
 
 	return rc;
-- 
2.43.0