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Message-ID: <alpine.LFD.2.11.1701262241280.3892@ja.home.ssi.bg>
Date: Thu, 26 Jan 2017 22:49:10 +0200 (EET)
From: Julian Anastasov <ja@....bg>
To: David Windsor <dwindsor@...il.com>
cc: netdev@...r.kernel.org, kernel-hardening@...ts.openwall.com,
netfilter-devel@...r.kernel.org, lvs-devel@...r.kernel.org,
wensong@...ux-vs.org, horms@...ge.net.au, pablo@...filter.org,
keescook@...omium.org, elena.reshetova@...el.com, ishkamiel@...il.com
Subject: Re: [PATCH v2 net] net: free ip_vs_dest structs when refcnt=0
Hello,
On Mon, 23 Jan 2017, David Windsor wrote:
> Currently, the ip_vs_dest cache frees ip_vs_dest objects when their
> reference count becomes < 0. Aside from not being semantically sound,
> this is problematic for the new type refcount_t, which will be introduced
> shortly in a separate patch. refcount_t is the new kernel type for
> holding reference counts, and provides overflow protection and a
> constrained interface relative to atomic_t (the type currently being
> used for kernel reference counts).
>
> Per Julian Anastasov: "The problem is that dest_trash currently holds
> deleted dests (unlinked from RCU lists) with refcnt=0." Changing
> dest_trash to hold dest with refcnt=1 will allow us to free ip_vs_dest
> structs when their refcnt=0, in ip_vs_dest_put_and_free().
>
> Signed-off-by: David Windsor <dwindsor@...il.com>
Thanks! I tested the first version and this one
just adds the needed changes in comments, so
Signed-off-by: Julian Anastasov <ja@....bg>
Simon and Pablo, this is more appropriate for
ipvs-next/nf-next. Please apply!
> ---
> include/net/ip_vs.h | 2 +-
> net/netfilter/ipvs/ip_vs_ctl.c | 8 +++-----
> 2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index cd6018a..a3e78ad 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -1421,7 +1421,7 @@ static inline void ip_vs_dest_put(struct ip_vs_dest *dest)
>
> static inline void ip_vs_dest_put_and_free(struct ip_vs_dest *dest)
> {
> - if (atomic_dec_return(&dest->refcnt) < 0)
> + if (atomic_dec_and_test(&dest->refcnt))
> kfree(dest);
> }
>
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 55e0169..5fc4836 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -711,7 +711,6 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, int dest_af,
> dest->vport == svc->port))) {
> /* HIT */
> list_del(&dest->t_list);
> - ip_vs_dest_hold(dest);
> goto out;
> }
> }
> @@ -741,7 +740,7 @@ static void ip_vs_dest_free(struct ip_vs_dest *dest)
> * When the ip_vs_control_clearup is activated by ipvs module exit,
> * the service tables must have been flushed and all the connections
> * are expired, and the refcnt of each destination in the trash must
> - * be 0, so we simply release them here.
> + * be 1, so we simply release them here.
> */
> static void ip_vs_trash_cleanup(struct netns_ipvs *ipvs)
> {
> @@ -1080,11 +1079,10 @@ static void __ip_vs_del_dest(struct netns_ipvs *ipvs, struct ip_vs_dest *dest,
> if (list_empty(&ipvs->dest_trash) && !cleanup)
> mod_timer(&ipvs->dest_trash_timer,
> jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));
> - /* dest lives in trash without reference */
> + /* dest lives in trash with reference */
> list_add(&dest->t_list, &ipvs->dest_trash);
> dest->idle_start = 0;
> spin_unlock_bh(&ipvs->dest_trash_lock);
> - ip_vs_dest_put(dest);
> }
>
>
> @@ -1160,7 +1158,7 @@ static void ip_vs_dest_trash_expire(unsigned long data)
>
> spin_lock(&ipvs->dest_trash_lock);
> list_for_each_entry_safe(dest, next, &ipvs->dest_trash, t_list) {
> - if (atomic_read(&dest->refcnt) > 0)
> + if (atomic_read(&dest->refcnt) > 1)
> continue;
> if (dest->idle_start) {
> if (time_before(now, dest->idle_start +
> --
> 2.7.4
Regards
--
Julian Anastasov <ja@....bg>
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