Re: [PATCH i-g-t] lib/igt_list: igt_list_empty() Detect uninitialized list

["Manszewski, Christoph" <christoph.manszewski@intel.com>]

Hi Peter,

On 22.09.2025 18:23, Peter Senna Tschudin wrote:
> Add a check to igt_list_empty() to return true if the list head pointer
> or its next/prev pointers are NULL, preventing segfaults when operating
> on uninitialized or potentially broken lists.
> 
> Signed-off-by: Peter Senna Tschudin <peter.senna@linux.intel.com>
> ---
>   lib/igt_list.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/lib/igt_list.c b/lib/igt_list.c
> index 37ae139c4..f77aef7dd 100644
> --- a/lib/igt_list.c
> +++ b/lib/igt_list.c
> @@ -79,5 +79,9 @@ int igt_list_length(const struct igt_list_head *head)
>   
>   bool igt_list_empty(const struct igt_list_head *head)
>   {
> +	/* Detect uninitialized / potentially broken list */
> +	if (!head || !head->next || !head->prev)
> +		return true;
> +

Without this change:
1. Passing an uninitialized list is a bug
2. The function doesn't check any condition and returns 'normally' 
regardless

With this change:
1. Passing an uninitialized list is a bug (still)
2. The function *may* detect an uninitialized list which is a bug but 
returns 'normally' regardless

If we are adding a check that catches some invalid/buggy condition the 
reasonable thing to do would be to assert/abort.

Regards,
Christoph


>   	return head->next == head;
>   }