[PATCH] virtio_ring: fix uninitialized used value

[PATCH] virtio_ring: fix uninitialized used value

[Jason Wang]

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@linaro.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
---
 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

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@linaro.org>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: kernelci.org bot <bot@kernelci.org>
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>

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

Re: [PATCH] virtio_ring: fix uninitialized used value

[Jason Wang]

On Fri, Jul 25, 2025 at 9:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> 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@linaro.org>
> > Cc: Randy Dunlap <rdunlap@infradead.org>
> > Reported-by: kernelci.org bot <bot@kernelci.org>
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
>
> I squashed but I think you should respin.
> also noticed a couple of minor issues.
>

I think a reppin of this patch should be sufficient.

I can post a new version.

Thanks