LVS
lvs-devel
Google
 
Web LinuxVirtualServer.org

Re: [PATCH 4/4] ipvs: reduce kernel stack usage

To: Arnd Bergmann <arnd@xxxxxxxx>
Subject: Re: [PATCH 4/4] ipvs: reduce kernel stack usage
Cc: Kees Cook <keescook@xxxxxxxxxxxx>, Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>, Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx>, Florian Westphal <fw@xxxxxxxxx>, James Smart <james.smart@xxxxxxxxxxxx>, Dick Kennedy <dick.kennedy@xxxxxxxxxxxx>, "James E . J . Bottomley" <jejb@xxxxxxxxxxxxx>, "Martin K . Petersen" <martin.petersen@xxxxxxxxxx>, Larry Finger <Larry.Finger@xxxxxxxxxxxx>, Florian Schilhabel <florian.c.schilhabel@xxxxxxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, James Morris <jmorris@xxxxxxxxx>, linux-scsi@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, devel@xxxxxxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
From: Julian Anastasov <ja@xxxxxx>
Date: Sun, 30 Jun 2019 23:36:41 +0300 (EEST)
        Hello,

On Fri, 28 Jun 2019, Arnd Bergmann wrote:

> With the new CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL option, the stack
> usage in the ipvs debug output grows because each instance of
> IP_VS_DBG_BUF() now has its own buffer of 160 bytes that add up
> rather than reusing the stack slots:
> 
> net/netfilter/ipvs/ip_vs_core.c: In function 'ip_vs_sched_persist':
> net/netfilter/ipvs/ip_vs_core.c:427:1: error: the frame size of 1052 bytes is 
> larger than 1024 bytes [-Werror=frame-larger-than=]
> net/netfilter/ipvs/ip_vs_core.c: In function 'ip_vs_new_conn_out':
> net/netfilter/ipvs/ip_vs_core.c:1231:1: error: the frame size of 1048 bytes 
> is larger than 1024 bytes [-Werror=frame-larger-than=]
> net/netfilter/ipvs/ip_vs_ftp.c: In function 'ip_vs_ftp_out':
> net/netfilter/ipvs/ip_vs_ftp.c:397:1: error: the frame size of 1104 bytes is 
> larger than 1024 bytes [-Werror=frame-larger-than=]
> net/netfilter/ipvs/ip_vs_ftp.c: In function 'ip_vs_ftp_in':
> net/netfilter/ipvs/ip_vs_ftp.c:555:1: error: the frame size of 1200 bytes is 
> larger than 1024 bytes [-Werror=frame-larger-than=]
> 
> Since printk() already has a way to print IPv4/IPv6 addresses using
> the %pIS format string, use that instead, combined with a macro that
> creates a local sockaddr structure on the stack. These will still
> add up, but the stack frames are now under 200 bytes.
> 
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> I'm not sure this actually does what I think it does. Someone
> needs to verify that we correctly print the addresses here.
> I've also only added three files that caused the warning messages
> to be reported. There are still a lot of other instances of
> IP_VS_DBG_BUF() that could be converted the same way after the
> basic idea is confirmed.
> ---
>  include/net/ip_vs.h             | 71 +++++++++++++++++++--------------
>  net/netfilter/ipvs/ip_vs_core.c | 44 ++++++++++----------
>  net/netfilter/ipvs/ip_vs_ftp.c  | 20 +++++-----
>  3 files changed, 72 insertions(+), 63 deletions(-)
> 
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index 3759167f91f5..3dfbeef67be6 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -227,6 +227,16 @@ static inline const char *ip_vs_dbg_addr(int af, char 
> *buf, size_t buf_len,
>                      sizeof(ip_vs_dbg_buf), addr,                     \
>                      &ip_vs_dbg_idx)
>  
> +#define IP_VS_DBG_SOCKADDR4(fam, addr, port)                         \
> +     (struct sockaddr*)&(struct sockaddr_in)                         \
> +     { .sin_family = (fam), .sin_addr = (addr)->in, .sin_port = (port) }
> +#define IP_VS_DBG_SOCKADDR6(fam, addr, port)                         \
> +     (struct sockaddr*)&(struct sockaddr_in6) \
> +     { .sin6_family = (fam), .sin6_addr = (addr)->in6, .sin6_port = (port) }
> +#define IP_VS_DBG_SOCKADDR(fam, addr, port) (fam == AF_INET ?                
> \
> +                     IP_VS_DBG_SOCKADDR4(fam, addr, port) :          \
> +                     IP_VS_DBG_SOCKADDR6(fam, addr, port))
> +
>  #define IP_VS_DBG(level, msg, ...)                                   \
>       do {                                                            \
>               if (level <= ip_vs_get_debug_level())                   \
> @@ -251,6 +261,7 @@ static inline const char *ip_vs_dbg_addr(int af, char 
> *buf, size_t buf_len,
>  #else        /* NO DEBUGGING at ALL */
>  #define IP_VS_DBG_BUF(level, msg...)  do {} while (0)
>  #define IP_VS_ERR_BUF(msg...)  do {} while (0)
> +#define IP_VS_DBG_SOCKADDR(fam, addr, port) NULL
>  #define IP_VS_DBG(level, msg...)  do {} while (0)
>  #define IP_VS_DBG_RL(msg...)  do {} while (0)
>  #define IP_VS_DBG_PKT(level, af, pp, skb, ofs, msg)  do {} while (0)
> @@ -1244,31 +1255,31 @@ static inline void ip_vs_control_del(struct 
> ip_vs_conn *cp)
>  {
>       struct ip_vs_conn *ctl_cp = cp->control;
>       if (!ctl_cp) {
> -             IP_VS_ERR_BUF("request control DEL for uncontrolled: "
> -                           "%s:%d to %s:%d\n",
> -                           IP_VS_DBG_ADDR(cp->af, &cp->caddr),
> -                           ntohs(cp->cport),
> -                           IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
> -                           ntohs(cp->vport));
> +             pr_err("request control DEL for uncontrolled: "
> +                    "%pISp to %pISp\n",

        ip_vs_dbg_addr() used compact form (%pI6c), so it would be
better to use %pISc and %pISpc everywhere in IPVS...

        Also, note that before now port was printed with %d and
ntohs() was used, now port should be in network order, so:

- ntohs() should be removed
- htons() should be added, if missing. At first look, this case
is not present in IPVS, we have only ntohs() usage

Regards

--
Julian Anastasov <ja@xxxxxx>

<Prev in Thread] Current Thread [Next in Thread>