As gcc luckily noted:

On Tue, Aug 20, 2024 at 03:33:20PM +0800, Xuan Zhuo wrote:
> @@ -1617,23 +1617,24 @@ static void detach_buf_packed(struct vring_virtqueue 
> *vq,
>       }
>  
>       if (vq->indirect) {
> +             struct vring_desc_extra *extra;
>               u32 len;
>  
>               /* Free the indirect table, if any, now that it's unmapped. */
> -             desc = state->indir_desc;
> -             if (!desc)

desc is no longer initialized here

> +             extra = state->indir;
> +             if (!extra)
>                       return;
>  
>               if (vring_need_unmap_buffer(vq)) {
>                       len = vq->packed.desc_extra[id].len;
>                       for (i = 0; i < len / sizeof(struct vring_packed_desc);
>                                       i++)
> -                             vring_unmap_desc_packed(vq, &desc[i]);
> +                             vring_unmap_extra_packed(vq, &extra[i]);
>               }
>               kfree(desc);


but freed here

> -             state->indir_desc = NULL;
> +             state->indir = NULL;
>       } else if (ctx) {
> -             *ctx = state->indir_desc;
> +             *ctx = state->indir;
>       }
>  }


It seems unlikely this was always 0 on all paths with even
a small amount of stress, so now I question how this was tested.
Besides, do not ignore compiler warnings, and do not tweak code
to just make compiler shut up - they are your friend.

>  
> -- 
> 2.32.0.3.g01195cf9f


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