Re: [PATCH v2 net] ipvs: prevent integer overflow in do_ip_vs_get_ctl()

[Julian Anastasov <ja@xxxxxx>]

        Hello,

On Mon, 10 Mar 2025, Dan Carpenter wrote:

> The get->num_services variable is an unsigned int which is controlled by
> the user.  The struct_size() function ensures that the size calculation
> does not overflow an unsigned long, however, we are saving the result to
> an int so the calculation can overflow.
> 
> Both "len" and "get->num_services" come from the user.  This check is
> just a sanity check to help the user and ensure they are using the API
> correctly.  An integer overflow here is not a big deal.  This has no
> security impact.
> 
> Save the result from struct_size() type size_t to fix this integer
> overflow bug.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

        Looks good to me, thanks!

Acked-by: Julian Anastasov <ja@xxxxxx>

        Pablo, you can apply it to the nf tree.

> ---
> v2: fix %lu vs %zu in the printk().  It breaks the build on 32bit
>     systems.
>     Remove the CC stable.
> 
>  net/netfilter/ipvs/ip_vs_ctl.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 7d13110ce188..0633276d96bf 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -3091,12 +3091,12 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void 
> __user *user, int *len)
>       case IP_VS_SO_GET_SERVICES:
>       {
>               struct ip_vs_get_services *get;
> -             int size;
> +             size_t size;
>  
>               get = (struct ip_vs_get_services *)arg;
>               size = struct_size(get, entrytable, get->num_services);
>               if (*len != size) {
> -                     pr_err("length: %u != %u\n", *len, size);
> +                     pr_err("length: %u != %zu\n", *len, size);
>                       ret = -EINVAL;
>                       goto out;
>               }
> @@ -3132,12 +3132,12 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void 
> __user *user, int *len)
>       case IP_VS_SO_GET_DESTS:
>       {
>               struct ip_vs_get_dests *get;
> -             int size;
> +             size_t size;
>  
>               get = (struct ip_vs_get_dests *)arg;
>               size = struct_size(get, entrytable, get->num_dests);
>               if (*len != size) {
> -                     pr_err("length: %u != %u\n", *len, size);
> +                     pr_err("length: %u != %zu\n", *len, size);
>                       ret = -EINVAL;
>                       goto out;
>               }
> -- 
> 2.47.2

Regards

--
Julian Anastasov <ja@xxxxxx>