[Spice-devel] [linux-agent v1 4/5] x11: Avoid dereference of a null pointer

[Frediano Ziglio]

> 
> From: Victor Toso <me at victortoso.com>
> 
> Found by coverity:
>   | warning: Access to field 'next' results in a dereference of a
>   | null pointer (loaded from variable 'prev_sel')
> 
> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>  src/vdagent/x11.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/vdagent/x11.c b/src/vdagent/x11.c
> index c3c7a65..69eed4a 100644
> --- a/src/vdagent/x11.c
> +++ b/src/vdagent/x11.c
> @@ -394,7 +394,7 @@ static void vdagent_x11_set_clipboard_owner(struct
> vdagent_x11 *x11,
>                  x11->selection_req_data_pos = 0;
>                  x11->selection_req_data_size = 0;
>                  x11->selection_req_atom = None;
> -            } else {
> +            } else if (prev_sel != NULL) {
>                  prev_sel->next = next_sel;
>              }
>              free(curr_sel);

This is a false positive, if is not the first there's a previous.
Not that I have an easy suggestion on how to make Coverity understand this!
One way would be to change prev_sel to a pointer to the next so
initializing it like 

   struct vdagent_x11_selection_request **p_prev_next = &x11->selection_req;

and update with

   p_prev_next = &curr_sel->next;

Frediano