2021-09-29 19:47:24

by Gustavo A. R. Silva

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 <[email protected]>
---
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

2021-09-30 13:07:41

by Takashi Iwai

Subject: Re: [PATCH][next] ALSA: virtio: Replace zero-length array with flexible-array member

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 <[email protected]>

Thanks, applied.


Takashi