Re: [iproute PATCH v2 7/7] lib/ll_map: Make sure im->name is NULL-terminated

[Stephen Hemminger]

On Thu, 17 Aug 2017 19:09:32 +0200
Phil Sutter <p...@nwl.cc> wrote:

> Signed-off-by: Phil Sutter <p...@nwl.cc>
> ---
>  lib/ll_map.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/ll_map.c b/lib/ll_map.c
> index 4e4556c9ac80b..4d06eb69f138a 100644
> --- a/lib/ll_map.c
> +++ b/lib/ll_map.c
> @@ -120,11 +120,11 @@ int ll_remember_index(const struct sockaddr_nl *who,
>               return 0;
>       }
>  
> -     im = malloc(sizeof(*im));
> +     im = calloc(1, sizeof(*im));
>       if (im == NULL)
>               return 0;
>       im->index = ifi->ifi_index;
> -     strcpy(im->name, ifname);
> +     strncpy(im->name, ifname, IFNAMSIZ - 1);
>       im->type = ifi->ifi_type;
>       im->flags = ifi->ifi_flags;
>  

This is not really necessary. kernel won't return
an ifname with a length >= IFNAMSIZ.

If you wanted to future proof it, why not use variable size allocation

--- a/lib/ll_map.c
+++ b/lib/ll_map.c
@@ -30,7 +30,7 @@ struct ll_cache {
        unsigned        flags;
        unsigned        index;
        unsigned short  type;
-       char            name[IFNAMSIZ];
+       char            name[];
 };
 
 #define IDXMAP_SIZE    1024
@@ -120,7 +120,7 @@ int ll_remember_index(const struct sockaddr_nl *who,
                return 0;
        }
 
-       im = malloc(sizeof(*im));
+       im = malloc(sizeof(*im) + strlen(ifname) + 1);
        if (im == NULL)
                return 0;
        im->index = ifi->ifi_index;