netdev - Re: [PATCH net] ipvs: prevent integer overflow in do_ip_vs_get

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Message-ID: <a89fe1a8-989d-c2b7-f039-63670d099b67@ssi.bg>
Date: Sat, 8 Mar 2025 14:06:53 +0200 (EET)
From: Julian Anastasov <ja@....bg>
To: Dan Carpenter <dan.carpenter@...aro.org>
cc: "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Simon Horman <horms@...ge.net.au>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        lvs-devel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] ipvs: prevent integer overflow in
 do_ip_vs_get_ctl()


	Hello,

On Fri, 7 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.
> 
> Save the result from struct_size() type size_t to fix this integer
> overflow bug.
> 
> Cc: stable@...r.kernel.org
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  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..801d65fd8a81 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);

	Both are GET operations. The problem that can happen only
on 64-bit platforms is that user will attempt copy_to_user() with
shorter buffer and will get EFAULT if there are so many entries to
return. On 32-bit size will be -1 and will not match *len (EINVAL).
So, I assume the issue is not critical, right?

>  		if (*len != size) {
> -			pr_err("length: %u != %u\n", *len, size);
> +			pr_err("length: %u != %lu\n", *len, size);

	%zu, %lu fails on 32-bit platforms. Please, send v2
fixing the format.

>  			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 != %lu\n", *len, size);
>  			ret = -EINVAL;
>  			goto out;
>  		}
> -- 
> 2.47.2

Regards

--
Julian Anastasov <ja@....bg>