Hi Simon, Julian,
On Wed, Aug 27, 2014 at 03:20:43PM +0900, Simon Horman wrote:
> From: Julian Anastasov <ja@xxxxxx>
>
> 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@xxxxxx>
> CC: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> CC: Andrey Utkin <andrey.krieger.utkin@xxxxxxxxx>
> CC: David Binderman <dcb314@xxxxxxxxxxx>
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
> ---
> 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!
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