Re: [PATCH] virtio_ring: fix uninitialized used value

[Michael S. Tsirkin]

On Fri, Jul 25, 2025 at 04:36:35PM +0800, Jason Wang wrote:
> Buildbot reports uninitialized used:
> 
> drivers/virtio/virtio_ring.c:2113:40: error: variable 'id' is
> uninitialized when used here [-Werror,-Wuninitialized]
>  2113 |                 BAD_RING(vq, "id %u out of range\n", id);
>       |                                                      ^~
> drivers/virtio/virtio_ring.c:2077:19: note: initialize the variable
> 'id' to silence this warning
>  2077 |         u16 last_used, id, last_used_idx;
>       |                          ^
>       |                           = 0
> 1 error generated.
> 
> Fixing this by use last_used instead and drop the complete unused
> variable id.
> 
> Cc: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Reported-by: kernelci.org bot <bot@xxxxxxxxxxxx>
> Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>

I squashed but I think you should respin.
also noticed a couple of minor issues.

> ---
>  drivers/virtio/virtio_ring.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 8f9413acd4e2..7b960ce9a034 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2074,7 +2074,7 @@ static void *virtqueue_get_buf_ctx_packed_in_order(struct vring_virtqueue *vq,
>  						   void **ctx)
>  {
>  	unsigned int num = vq->packed.vring.num;
> -	u16 last_used, id, last_used_idx;
> +	u16 last_used, last_used_idx;
>  	bool used_wrap_counter;
>  	void *ret;
>  
> @@ -2110,11 +2110,11 @@ static void *virtqueue_get_buf_ctx_packed_in_order(struct vring_virtqueue *vq,
>  		*len = vq->packed.desc_state[last_used].total_len;
>  
>  	if (unlikely(last_used >= num)) {
> -		BAD_RING(vq, "id %u out of range\n", id);
> +		BAD_RING(vq, "id %u out of range\n", last_used);
>  		return NULL;
>  	}
>  	if (unlikely(!vq->packed.desc_state[last_used].data)) {
> -		BAD_RING(vq, "id %u is not a head!\n", id);
> +		BAD_RING(vq, "id %u is not a head!\n", last_used);
>  		return NULL;
>  	}
>  
> -- 
> 2.39.5