diff mbox

[nf-next] ipvs: reduce stack usage for sockopt data

Message ID 1409120443-978-2-git-send-email-horms@verge.net.au
State Awaiting Upstream, archived
Delegated to: David Miller
Headers show

Commit Message

Simon Horman Aug. 27, 2014, 6:20 a.m. UTC 
From: Julian Anastasov <ja@ssi.bg>

Use macros and union to reserve the required stack space for
sockopt data. Now the tables for commands should be more safe
to extend. The checks added for readability are optimized by
compiler, others warn at compile time if command uses too much
stack or exceeds the storage of set_arglen and get_arglen.

As Dan Carpenter points out, we can run for unprivileged user,
so we can silent some error messages.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
CC: Dan Carpenter <dan.carpenter@oracle.com>
CC: Andrey Utkin <andrey.krieger.utkin@gmail.com>
CC: David Binderman <dcb314@hotmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 102 +++++++++++++++++++++++------------------
 1 file changed, 57 insertions(+), 45 deletions(-)

Comments

Pablo Neira Ayuso Sept. 2, 2014, 11:31 a.m. UTC | #1 
Hi Simon, Julian,

On Wed, Aug 27, 2014 at 03:20:43PM +0900, Simon Horman wrote:
> From: Julian Anastasov <ja@ssi.bg>
> 
> Use macros and union to reserve the required stack space for
> sockopt data. Now the tables for commands should be more safe
> to extend. The checks added for readability are optimized by
> compiler, others warn at compile time if command uses too much
> stack or exceeds the storage of set_arglen and get_arglen.
> 
> As Dan Carpenter points out, we can run for unprivileged user,
> so we can silent some error messages.
> 
> Signed-off-by: Julian Anastasov <ja@ssi.bg>
> CC: Dan Carpenter <dan.carpenter@oracle.com>
> CC: Andrey Utkin <andrey.krieger.utkin@gmail.com>
> CC: David Binderman <dcb314@hotmail.com>
> Signed-off-by: Simon Horman <horms@verge.net.au>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c | 102 +++++++++++++++++++++++------------------
>  1 file changed, 57 insertions(+), 45 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index fd3f444..0140e09 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -2180,28 +2180,34 @@ static int ip_vs_set_timeout(struct net *net, struct ip_vs_timeout_user *u)
>  }
>  
>  
> -#define SET_CMDID(cmd)		(cmd - IP_VS_BASE_CTL)
> -#define SERVICE_ARG_LEN		(sizeof(struct ip_vs_service_user))
> -#define SVCDEST_ARG_LEN		(sizeof(struct ip_vs_service_user) +	\
> -				 sizeof(struct ip_vs_dest_user))
> -#define TIMEOUT_ARG_LEN		(sizeof(struct ip_vs_timeout_user))
> -#define DAEMON_ARG_LEN		(sizeof(struct ip_vs_daemon_user))
> -#define MAX_ARG_LEN		SVCDEST_ARG_LEN
> +#define SET_CMDID(cmd)			(cmd - IP_VS_BASE_CTL)
> +#define IP_VS_SET_CMDID(c, t)		[SET_CMDID(c)] = sizeof(t),
> +#define IP_VS_SET_CMDID_LEN(c, t)	t field_ ## c;
> +
> +struct ip_vs_svcdest_user {
> +	struct ip_vs_service_user	s;
> +	struct ip_vs_dest_user		d;
> +};
> +
> +#define IP_VS_SET_CMDID_TABLE(e)					\
> +	e(IP_VS_SO_SET_ADD,		struct ip_vs_service_user)	\
> +	e(IP_VS_SO_SET_EDIT,		struct ip_vs_service_user)	\
> +	e(IP_VS_SO_SET_DEL,		struct ip_vs_service_user)	\
> +	e(IP_VS_SO_SET_ADDDEST,		struct ip_vs_svcdest_user)	\
> +	e(IP_VS_SO_SET_DELDEST,		struct ip_vs_svcdest_user)	\
> +	e(IP_VS_SO_SET_EDITDEST,	struct ip_vs_svcdest_user)	\
> +	e(IP_VS_SO_SET_TIMEOUT,		struct ip_vs_timeout_user)	\
> +	e(IP_VS_SO_SET_STARTDAEMON,	struct ip_vs_daemon_user)	\
> +	e(IP_VS_SO_SET_STOPDAEMON,	struct ip_vs_daemon_user)	\
> +	e(IP_VS_SO_SET_ZERO,		struct ip_vs_service_user)
>  
>  static const unsigned char set_arglen[SET_CMDID(IP_VS_SO_SET_MAX)+1] = {
> -	[SET_CMDID(IP_VS_SO_SET_ADD)]		= SERVICE_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_EDIT)]		= SERVICE_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_DEL)]		= SERVICE_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_FLUSH)]		= 0,
> -	[SET_CMDID(IP_VS_SO_SET_ADDDEST)]	= SVCDEST_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_DELDEST)]	= SVCDEST_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_EDITDEST)]	= SVCDEST_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_TIMEOUT)]	= TIMEOUT_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_STARTDAEMON)]	= DAEMON_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_STOPDAEMON)]	= DAEMON_ARG_LEN,
> -	[SET_CMDID(IP_VS_SO_SET_ZERO)]		= SERVICE_ARG_LEN,
> +	IP_VS_SET_CMDID_TABLE(IP_VS_SET_CMDID)
>  };
>  
> +union ip_vs_set_arglen { IP_VS_SET_CMDID_TABLE(IP_VS_SET_CMDID_LEN) };

I see, basically, ip_vs_set_arglen expands to:

union ip_vs_set_arglen {
        struct struct ip_vs_service_user field_IP_VS_SO_SET_ADD;
        ...
};

> +#define MAX_SET_ARGLEN	sizeof(union ip_vs_set_arglen)

So MAX_SET_ARGLEN is set accordingly to allocate the maximum data size
that you can get from userspace in the stack, this seems correct to me.

I guess the target of these macros is to avoid code duplication, since
without the macros you also need:

static const unsigned char set_arglen[...] = {
        [SET_CMDID(IP_VS_SO_SET_ADD)] = sizeof(struct ip_vs_service_user),
        ...
};

which is quite similar to union ip_vs_set_arglen in the sense that
they relate the commands and the structure size in different ways.

However, unless this is saving us from more hassle that I'm
overlooking, I think it's better (in terms of readability) IMO to keep
the explicit definitions.

Let me know, thanks!
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index fd3f444..0140e09 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2180,28 +2180,34 @@  static int ip_vs_set_timeout(struct net *net, struct ip_vs_timeout_user *u)
 }
 
 
-#define SET_CMDID(cmd)		(cmd - IP_VS_BASE_CTL)
-#define SERVICE_ARG_LEN		(sizeof(struct ip_vs_service_user))
-#define SVCDEST_ARG_LEN		(sizeof(struct ip_vs_service_user) +	\
-				 sizeof(struct ip_vs_dest_user))
-#define TIMEOUT_ARG_LEN		(sizeof(struct ip_vs_timeout_user))
-#define DAEMON_ARG_LEN		(sizeof(struct ip_vs_daemon_user))
-#define MAX_ARG_LEN		SVCDEST_ARG_LEN
+#define SET_CMDID(cmd)			(cmd - IP_VS_BASE_CTL)
+#define IP_VS_SET_CMDID(c, t)		[SET_CMDID(c)] = sizeof(t),
+#define IP_VS_SET_CMDID_LEN(c, t)	t field_ ## c;
+
+struct ip_vs_svcdest_user {
+	struct ip_vs_service_user	s;
+	struct ip_vs_dest_user		d;
+};
+
+#define IP_VS_SET_CMDID_TABLE(e)					\
+	e(IP_VS_SO_SET_ADD,		struct ip_vs_service_user)	\
+	e(IP_VS_SO_SET_EDIT,		struct ip_vs_service_user)	\
+	e(IP_VS_SO_SET_DEL,		struct ip_vs_service_user)	\
+	e(IP_VS_SO_SET_ADDDEST,		struct ip_vs_svcdest_user)	\
+	e(IP_VS_SO_SET_DELDEST,		struct ip_vs_svcdest_user)	\
+	e(IP_VS_SO_SET_EDITDEST,	struct ip_vs_svcdest_user)	\
+	e(IP_VS_SO_SET_TIMEOUT,		struct ip_vs_timeout_user)	\
+	e(IP_VS_SO_SET_STARTDAEMON,	struct ip_vs_daemon_user)	\
+	e(IP_VS_SO_SET_STOPDAEMON,	struct ip_vs_daemon_user)	\
+	e(IP_VS_SO_SET_ZERO,		struct ip_vs_service_user)
 
 static const unsigned char set_arglen[SET_CMDID(IP_VS_SO_SET_MAX)+1] = {
-	[SET_CMDID(IP_VS_SO_SET_ADD)]		= SERVICE_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_EDIT)]		= SERVICE_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_DEL)]		= SERVICE_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_FLUSH)]		= 0,
-	[SET_CMDID(IP_VS_SO_SET_ADDDEST)]	= SVCDEST_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_DELDEST)]	= SVCDEST_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_EDITDEST)]	= SVCDEST_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_TIMEOUT)]	= TIMEOUT_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_STARTDAEMON)]	= DAEMON_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_STOPDAEMON)]	= DAEMON_ARG_LEN,
-	[SET_CMDID(IP_VS_SO_SET_ZERO)]		= SERVICE_ARG_LEN,
+	IP_VS_SET_CMDID_TABLE(IP_VS_SET_CMDID)
 };
 
+union ip_vs_set_arglen { IP_VS_SET_CMDID_TABLE(IP_VS_SET_CMDID_LEN) };
+#define MAX_SET_ARGLEN	sizeof(union ip_vs_set_arglen)
+
 static void ip_vs_copy_usvc_compat(struct ip_vs_service_user_kern *usvc,
 				  struct ip_vs_service_user *usvc_compat)
 {
@@ -2239,7 +2245,7 @@  do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 {
 	struct net *net = sock_net(sk);
 	int ret;
-	unsigned char arg[MAX_ARG_LEN];
+	unsigned char arg[MAX_SET_ARGLEN];
 	struct ip_vs_service_user *usvc_compat;
 	struct ip_vs_service_user_kern usvc;
 	struct ip_vs_service *svc;
@@ -2247,16 +2253,15 @@  do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 	struct ip_vs_dest_user_kern udest;
 	struct netns_ipvs *ipvs = net_ipvs(net);
 
+	BUILD_BUG_ON(sizeof(arg) > 255);
 	if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
 
 	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_SET_MAX)
 		return -EINVAL;
-	if (len < 0 || len >  MAX_ARG_LEN)
-		return -EINVAL;
 	if (len != set_arglen[SET_CMDID(cmd)]) {
-		pr_err("set_ctl: len %u != %u\n",
-		       len, set_arglen[SET_CMDID(cmd)]);
+		IP_VS_DBG(1, "set_ctl: len %u != %u\n",
+			  len, set_arglen[SET_CMDID(cmd)]);
 		return -EINVAL;
 	}
 
@@ -2513,49 +2518,56 @@  __ip_vs_get_timeouts(struct net *net, struct ip_vs_timeout_user *u)
 }
 
 
-#define GET_CMDID(cmd)		(cmd - IP_VS_BASE_CTL)
-#define GET_INFO_ARG_LEN	(sizeof(struct ip_vs_getinfo))
-#define GET_SERVICES_ARG_LEN	(sizeof(struct ip_vs_get_services))
-#define GET_SERVICE_ARG_LEN	(sizeof(struct ip_vs_service_entry))
-#define GET_DESTS_ARG_LEN	(sizeof(struct ip_vs_get_dests))
-#define GET_TIMEOUT_ARG_LEN	(sizeof(struct ip_vs_timeout_user))
-#define GET_DAEMON_ARG_LEN	(sizeof(struct ip_vs_daemon_user) * 2)
+#define GET_CMDID(cmd)			(cmd - IP_VS_BASE_CTL)
+#define IP_VS_GET_CMDID(c, t)		[GET_CMDID(c)] = sizeof(t),
+#define IP_VS_GET_CMDID_LEN(c, t)	t field_ ## c;
+
+struct ip_vs_version_user {
+	char	v[64];
+};
+
+struct ip_vs_daemon_user2 {
+	struct ip_vs_daemon_user	d1, d2;
+};
+
+#define IP_VS_GET_CMDID_TABLE(e)					\
+	e(IP_VS_SO_GET_VERSION,		struct ip_vs_version_user)	\
+	e(IP_VS_SO_GET_INFO,		struct ip_vs_getinfo)		\
+	e(IP_VS_SO_GET_SERVICES,	struct ip_vs_get_services)	\
+	e(IP_VS_SO_GET_SERVICE,		struct ip_vs_service_entry)	\
+	e(IP_VS_SO_GET_DESTS,		struct ip_vs_get_dests)		\
+	e(IP_VS_SO_GET_TIMEOUT,		struct ip_vs_timeout_user)	\
+	e(IP_VS_SO_GET_DAEMON,		struct ip_vs_daemon_user2)
 
 static const unsigned char get_arglen[GET_CMDID(IP_VS_SO_GET_MAX)+1] = {
-	[GET_CMDID(IP_VS_SO_GET_VERSION)]	= 64,
-	[GET_CMDID(IP_VS_SO_GET_INFO)]		= GET_INFO_ARG_LEN,
-	[GET_CMDID(IP_VS_SO_GET_SERVICES)]	= GET_SERVICES_ARG_LEN,
-	[GET_CMDID(IP_VS_SO_GET_SERVICE)]	= GET_SERVICE_ARG_LEN,
-	[GET_CMDID(IP_VS_SO_GET_DESTS)]		= GET_DESTS_ARG_LEN,
-	[GET_CMDID(IP_VS_SO_GET_TIMEOUT)]	= GET_TIMEOUT_ARG_LEN,
-	[GET_CMDID(IP_VS_SO_GET_DAEMON)]	= GET_DAEMON_ARG_LEN,
+	IP_VS_GET_CMDID_TABLE(IP_VS_GET_CMDID)
 };
 
+union ip_vs_get_arglen { IP_VS_GET_CMDID_TABLE(IP_VS_GET_CMDID_LEN) };
+#define MAX_GET_ARGLEN	sizeof(union ip_vs_get_arglen)
+
 static int
 do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
 {
-	unsigned char arg[128];
+	unsigned char arg[MAX_GET_ARGLEN];
 	int ret = 0;
 	unsigned int copylen;
 	struct net *net = sock_net(sk);
 	struct netns_ipvs *ipvs = net_ipvs(net);
 
 	BUG_ON(!net);
+	BUILD_BUG_ON(sizeof(arg) > 255);
 	if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
 
 	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_GET_MAX)
 		return -EINVAL;
 
-	if (*len < get_arglen[GET_CMDID(cmd)]) {
-		pr_err("get_ctl: len %u < %u\n",
-		       *len, get_arglen[GET_CMDID(cmd)]);
-		return -EINVAL;
-	}
-
 	copylen = get_arglen[GET_CMDID(cmd)];
-	if (copylen > 128)
+	if (*len < (int) copylen || *len < 0) {
+		IP_VS_DBG(1, "get_ctl: len %d < %u\n", *len, copylen);
 		return -EINVAL;
+	}
 
 	if (copy_from_user(arg, user, copylen) != 0)
 		return -EFAULT;