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* [PATCH][next] ALSA: virtio: Replace zero-length array with flexible-array member
@ 2021-09-29 19:15 Gustavo A. R. Silva
  2021-09-30 11:48 ` Takashi Iwai
  0 siblings, 1 reply; 2+ messages in thread
From: Gustavo A. R. Silva @ 2021-09-29 19:15 UTC (permalink / raw)
  To: Anton Yakovlev, Michael S. Tsirkin, Jaroslav Kysela, Takashi Iwai
  Cc: virtualization, alsa-devel, linux-kernel, Gustavo A. R. Silva,
	linux-hardening

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@kernel.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


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH][next] ALSA: virtio: Replace zero-length array with flexible-array member
  2021-09-29 19:15 [PATCH][next] ALSA: virtio: Replace zero-length array with flexible-array member Gustavo A. R. Silva
@ 2021-09-30 11:48 ` Takashi Iwai
  0 siblings, 0 replies; 2+ messages in thread
From: Takashi Iwai @ 2021-09-30 11:48 UTC (permalink / raw)
  To: Gustavo A. R. Silva
  Cc: Anton Yakovlev, Michael S. Tsirkin, Jaroslav Kysela,
	Takashi Iwai, virtualization, alsa-devel, linux-kernel,
	linux-hardening

On Wed, 29 Sep 2021 21:15:04 +0200,
Gustavo A. R. Silva wrote:
> 
> 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@kernel.org>

Thanks, applied.


Takashi

^ permalink raw reply	[flat|nested] 2+ messages in thread

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