Re: [PATCH v3] netfilter/ipset: replace a strncpy() with strscpy()

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Hi,

On Sat, 1 Dec 2018, Qian Cai wrote:

> To make overflows as obvious as possible and to prevent code from blithely
> proceeding with a truncated string. This also has a side-effect to fix a
> compilation warning when using GCC 8.2.1.
> 
> net/netfilter/ipset/ip_set_core.c: In function 'ip_set_sockfn_get':
> net/netfilter/ipset/ip_set_core.c:2027:3: warning: 'strncpy' writing 32
> bytes into a region of size 2 overflows the destination
> [-Wstringop-overflow=]
> 
> Signed-off-by: Qian Cai <cai@xxxxxx>

Patch is applied with a slight modification, see below:
 
> Changelog:
> * v2:
> - Released the lock for the error-path as well.
> * v1:
> - Checked the return value.
> 
>  net/netfilter/ipset/ip_set_core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
> index 1577f2f76060..33929fb645b6 100644
> --- a/net/netfilter/ipset/ip_set_core.c
> +++ b/net/netfilter/ipset/ip_set_core.c
> @@ -2024,9 +2024,11 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user *user, int *len)
>  		}
>  		nfnl_lock(NFNL_SUBSYS_IPSET);
>  		set = ip_set(inst, req_get->set.index);
> -		strncpy(req_get->set.name, set ? set->name : "",
> -			IPSET_MAXNAMELEN);
> +		ret = strscpy(req_get->set.name, set ? set->name : "",
> +			      IPSET_MAXNAMELEN);
>  		nfnl_unlock(NFNL_SUBSYS_IPSET);
> +		if (ret == -E2BIG)

I replaced the condition with

		if (ret < 0)

so that it can handle future error codes from strscpy() as well.

> +			goto done;
>  		goto copy;
>  	}
>  	default:

Best regards,
Jozsef
-
E-mail  : kadlec@xxxxxxxxxxxxxxxxx, kadlecsik.jozsef@xxxxxxxxxxxxx
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary



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