linux-hardening - [PATCH][next] ALSA: virtio: Replace zero-length array with flexible-array member

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Message-ID: <20210929191504.GA337268@embeddedor>
Date:   Wed, 29 Sep 2021 14:15:04 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Anton Yakovlev <anton.yakovlev@...nsynergy.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     virtualization@...ts.linux-foundation.org,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] ALSA: virtio: Replace zero-length array with
 flexible-array member

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

Also, make use of the struct_size() helper in kzalloc().

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/78
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 sound/virtio/virtio_pcm_msg.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/sound/virtio/virtio_pcm_msg.c b/sound/virtio/virtio_pcm_msg.c
index f88c8f29cbd8..aca2dc1989ba 100644
--- a/sound/virtio/virtio_pcm_msg.c
+++ b/sound/virtio/virtio_pcm_msg.c
@@ -20,7 +20,7 @@ struct virtio_pcm_msg {
 	struct virtio_snd_pcm_xfer xfer;
 	struct virtio_snd_pcm_status status;
 	size_t length;
-	struct scatterlist sgs[0];
+	struct scatterlist sgs[];
 };
 
 /**
@@ -146,8 +146,7 @@ int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss,
 		int sg_num = virtsnd_pcm_sg_num(data, period_bytes);
 		struct virtio_pcm_msg *msg;
 
-		msg = kzalloc(sizeof(*msg) + sizeof(*msg->sgs) * (sg_num + 2),
-			      GFP_KERNEL);
+		msg = kzalloc(struct_size(msg, sgs, sg_num + 2), GFP_KERNEL);
 		if (!msg)
 			return -ENOMEM;
 
-- 
2.27.0