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Message-Id: <1485262100-12366-1-git-send-email-dwindsor@gmail.com> Date: Tue, 24 Jan 2017 07:48:20 -0500 From: David Windsor <dwindsor@...il.com> To: netdev@...r.kernel.org, kernel-hardening@...ts.openwall.com Cc: keescook@...omium.org, elena.reshetova@...el.com, ja@....bg, dwindsor@...il.com, ishkamiel@...il.com Subject: [PATCH net] net: free ip_vs_dest structs when refcnt=0 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 Juilan 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> --- include/net/ip_vs.h | 2 +- net/netfilter/ipvs/ip_vs_ctl.c | 4 +--- 2 files changed, 2 insertions(+), 4 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..6b5492e 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; } } @@ -1084,7 +1083,6 @@ static void __ip_vs_del_dest(struct netns_ipvs *ipvs, struct ip_vs_dest *dest, 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
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