Re: [PATCH] libipvs: fix some buffer sizes

[Jesper Dangaard Brouer <brouer@redhat.com>]

On Thu, 24 May 2018 23:37:45 +0300 Julian Anastasov <ja@ssi.bg> wrote:

> Size or length? Here is the answer:
> 
> - IP_VS_SCHEDNAME_MAXLEN and IP_VS_IFNAME_MAXLEN are sizes
> because they are used in kernel structures exported to user
> space for the old setsockopt interface. We can not change
> these structures in the kernel.
> 
> - IP_VS_PENAME_MAXLEN and IP_VS_PEDATA_MAXLEN are max lengths
> because they are not exported to the old interface.
> 
> As result:
> - buffers should have space for NUL terminator
> - strncpy should use sizeof(buffer) - 1 as max length
> 
> As we change the libipvs structures, their users should be
> recompiled.
> 
> Signed-off-by: Julian Anastasov <ja@ssi.bg>

This all looks fine to me.  I'll give other people a little time to
review and ACK, before I apply this.

(To Julian) did you find this by manual review, or did you use some tool
to find these?

> ---
>  ipvsadm.c         | 8 ++++----
>  libipvs/ip_vs.h   | 4 ++--
>  libipvs/libipvs.c | 7 ++++---
>  3 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/ipvsadm.c b/ipvsadm.c
> index 1a28d72..7695006 100644
> --- a/ipvsadm.c
> +++ b/ipvsadm.c
> @@ -595,7 +595,7 @@ parse_options(int argc, char **argv, struct ipvs_command_entry *ce,
>  		case 's':
>  			set_option(options, OPT_SCHEDULER);
>  			strncpy(ce->svc.sched_name,
> -				optarg, IP_VS_SCHEDNAME_MAXLEN);
> +				optarg, IP_VS_SCHEDNAME_MAXLEN - 1);
>  			break;
>  		case 'p':
>  			set_option(options, OPT_PERSISTENT);
> @@ -670,7 +670,7 @@ parse_options(int argc, char **argv, struct ipvs_command_entry *ce,
>  		case TAG_MCAST_INTERFACE:
>  			set_option(options, OPT_MCAST);
>  			strncpy(ce->daemon.mcast_ifn,
> -				optarg, IP_VS_IFNAME_MAXLEN);
> +				optarg, IP_VS_IFNAME_MAXLEN - 1);
>  			break;
>  		case 'I':
>  			set_option(options, OPT_SYNCID);
> @@ -1415,8 +1415,8 @@ static void print_conn(char *buf, unsigned int format)
>  	unsigned int    expires;
>  	unsigned short  af = AF_INET;
>  	unsigned short  daf = AF_INET;
> -	char		pe_name[IP_VS_PENAME_MAXLEN];
> -	char		pe_data[IP_VS_PEDATA_MAXLEN];
> +	char		pe_name[IP_VS_PENAME_MAXLEN + 1];
> +	char		pe_data[IP_VS_PEDATA_MAXLEN + 1];
>  
>  	int n;
>  	char temp1[INET6_ADDRSTRLEN], temp2[INET6_ADDRSTRLEN], temp3[INET6_ADDRSTRLEN];
> diff --git a/libipvs/ip_vs.h b/libipvs/ip_vs.h
> index 774ff96..e57d55a 100644
> --- a/libipvs/ip_vs.h
> +++ b/libipvs/ip_vs.h
> @@ -144,7 +144,7 @@ struct ip_vs_service_user {
>  	__be32			netmask;	/* persistent netmask */
>  	u_int16_t		af;
>  	union nf_inet_addr	addr;
> -	char			pe_name[IP_VS_PENAME_MAXLEN];
> +	char			pe_name[IP_VS_PENAME_MAXLEN + 1];
>  };
>  
>  struct ip_vs_dest_kern {
> @@ -267,7 +267,7 @@ struct ip_vs_service_entry {
>  
>  	u_int16_t		af;
>  	union nf_inet_addr	addr;
> -	char			pe_name[IP_VS_PENAME_MAXLEN];
> +	char			pe_name[IP_VS_PENAME_MAXLEN + 1];
>  
>  	/* statistics, 64-bit */
>  	struct ip_vs_stats64	stats64;
> diff --git a/libipvs/libipvs.c b/libipvs/libipvs.c
> index a843243..9be7700 100644
> --- a/libipvs/libipvs.c
> +++ b/libipvs/libipvs.c
> @@ -719,7 +719,7 @@ static int ipvs_services_parse_cb(struct nl_msg *msg, void *arg)
>  
>  	strncpy(get->entrytable[i].sched_name,
>  		nla_get_string(svc_attrs[IPVS_SVC_ATTR_SCHED_NAME]),
> -		IP_VS_SCHEDNAME_MAXLEN);
> +		IP_VS_SCHEDNAME_MAXLEN - 1);
>  
>  	if (svc_attrs[IPVS_SVC_ATTR_PE_NAME])
>  		strncpy(get->entrytable[i].pe_name,
> @@ -1199,7 +1199,7 @@ static int ipvs_daemon_parse_cb(struct nl_msg *msg, void *arg)
>  	u[i].state = nla_get_u32(daemon_attrs[IPVS_DAEMON_ATTR_STATE]);
>  	strncpy(u[i].mcast_ifn,
>  		nla_get_string(daemon_attrs[IPVS_DAEMON_ATTR_MCAST_IFN]),
> -		IP_VS_IFNAME_MAXLEN);
> +		IP_VS_IFNAME_MAXLEN - 1);
>  	u[i].syncid = nla_get_u32(daemon_attrs[IPVS_DAEMON_ATTR_SYNC_ID]);
>  
>  	a = daemon_attrs[IPVS_DAEMON_ATTR_SYNC_MAXLEN];
> @@ -1265,7 +1265,8 @@ ipvs_daemon_t *ipvs_get_daemon(void)
>  	}
>  	for (i = 0; i < 2; i++) {
>  		u[i].state = dmk[i].state;
> -		strncpy(u[i].mcast_ifn, dmk[i].mcast_ifn, IP_VS_IFNAME_MAXLEN);
> +		strncpy(u[i].mcast_ifn, dmk[i].mcast_ifn,
> +			IP_VS_IFNAME_MAXLEN - 1);
>  		u[i].syncid = dmk[i].syncid;
>  	}
>  	return u;



-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer