linux-kernel - Re: [PATCH] fix build error in function vfio_combine_iova

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Date:   Mon, 11 Sep 2023 12:44:31 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Cong Liu <liucong2@...inos.cn>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix build error in function vfio_combine_iova_ranges

On Mon, 11 Sep 2023 17:41:02 +0800
Cong Liu <liucong2@...inos.cn> wrote:

> when compiling with smatch check, the following errors were encountered:
> 
> drivers/vfio/vfio_main.c:957 vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
> 
> this patch fix these error.
> 
> Signed-off-by: Cong Liu <liucong2@...inos.cn>
> ---
>  drivers/vfio/vfio_main.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 40732e8ed4c6..0a9620409696 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -938,12 +938,13 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
>  void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
>  			      u32 req_nodes)
>  {
> -	struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
> +	struct interval_tree_node *prev, *curr;
> +	struct interval_tree_node *comb_start, *comb_end;

This looks cosmetic, what did it fix?  It's not clear to me how any of
this addresses the last two errors.  Thanks,

Alex

>  	unsigned long min_gap, curr_gap;
>  
>  	/* Special shortcut when a single range is required */
>  	if (req_nodes == 1) {
> -		unsigned long last;
> +		unsigned long last = 0;
>  
>  		comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
>  		curr = comb_start;