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ipvs: fix crash if scheduler is changed
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I overlooked the svc->sched_data usage from schedulers
when the services were converted to RCU in 3.10. Now
the rare ipvsadm -E command can change the scheduler
but due to the reverse order of ip_vs_bind_scheduler
and ip_vs_unbind_scheduler we provide new sched_data
to the old scheduler resulting in a crash.

To fix it without changing the scheduler methods we
have to use synchronize_rcu() only for the editing case.
It means all svc->scheduler readers should expect a
NULL value. To avoid breakage for the service listing
and ipvsadm -R we can use the "none" name to indicate
that scheduler is not assigned, a state when we drop
new connections.

Reported-by: Alexander Vasiliev <a.vasylev@404-group.com>
Fixes: ceec4c3 ("ipvs: convert services to rcu")
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
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Julian Anastasov authored and horms committed Jul 14, 2015
1 parent 4754957 commit 05f0050
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Showing 3 changed files with 69 additions and 37 deletions.
16 changes: 14 additions & 2 deletions net/netfilter/ipvs/ip_vs_core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -319,7 +319,13 @@ ip_vs_sched_persist(struct ip_vs_service *svc,
* return *ignored=0 i.e. ICMP and NF_DROP
*/
sched = rcu_dereference(svc->scheduler);
dest = sched->schedule(svc, skb, iph);
if (sched) {
/* read svc->sched_data after svc->scheduler */
smp_rmb();
dest = sched->schedule(svc, skb, iph);
} else {
dest = NULL;
}
if (!dest) {
IP_VS_DBG(1, "p-schedule: no dest found.\n");
kfree(param.pe_data);
Expand Down Expand Up @@ -467,7 +473,13 @@ ip_vs_schedule(struct ip_vs_service *svc, struct sk_buff *skb,
}

sched = rcu_dereference(svc->scheduler);
dest = sched->schedule(svc, skb, iph);
if (sched) {
/* read svc->sched_data after svc->scheduler */
smp_rmb();
dest = sched->schedule(svc, skb, iph);
} else {
dest = NULL;
}
if (dest == NULL) {
IP_VS_DBG(1, "Schedule: no dest found.\n");
return NULL;
Expand Down
78 changes: 49 additions & 29 deletions net/netfilter/ipvs/ip_vs_ctl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -842,15 +842,16 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest,
__ip_vs_dst_cache_reset(dest);
spin_unlock_bh(&dest->dst_lock);

sched = rcu_dereference_protected(svc->scheduler, 1);
if (add) {
ip_vs_start_estimator(svc->net, &dest->stats);
list_add_rcu(&dest->n_list, &svc->destinations);
svc->num_dests++;
if (sched->add_dest)
sched = rcu_dereference_protected(svc->scheduler, 1);
if (sched && sched->add_dest)
sched->add_dest(svc, dest);
} else {
if (sched->upd_dest)
sched = rcu_dereference_protected(svc->scheduler, 1);
if (sched && sched->upd_dest)
sched->upd_dest(svc, dest);
}
}
Expand Down Expand Up @@ -1084,7 +1085,7 @@ static void __ip_vs_unlink_dest(struct ip_vs_service *svc,
struct ip_vs_scheduler *sched;

sched = rcu_dereference_protected(svc->scheduler, 1);
if (sched->del_dest)
if (sched && sched->del_dest)
sched->del_dest(svc, dest);
}
}
Expand Down Expand Up @@ -1175,11 +1176,14 @@ ip_vs_add_service(struct net *net, struct ip_vs_service_user_kern *u,
ip_vs_use_count_inc();

/* Lookup the scheduler by 'u->sched_name' */
sched = ip_vs_scheduler_get(u->sched_name);
if (sched == NULL) {
pr_info("Scheduler module ip_vs_%s not found\n", u->sched_name);
ret = -ENOENT;
goto out_err;
if (strcmp(u->sched_name, "none")) {
sched = ip_vs_scheduler_get(u->sched_name);
if (!sched) {
pr_info("Scheduler module ip_vs_%s not found\n",
u->sched_name);
ret = -ENOENT;
goto out_err;
}
}

if (u->pe_name && *u->pe_name) {
Expand Down Expand Up @@ -1240,10 +1244,12 @@ ip_vs_add_service(struct net *net, struct ip_vs_service_user_kern *u,
spin_lock_init(&svc->stats.lock);

/* Bind the scheduler */
ret = ip_vs_bind_scheduler(svc, sched);
if (ret)
goto out_err;
sched = NULL;
if (sched) {
ret = ip_vs_bind_scheduler(svc, sched);
if (ret)
goto out_err;
sched = NULL;
}

/* Bind the ct retriever */
RCU_INIT_POINTER(svc->pe, pe);
Expand Down Expand Up @@ -1291,17 +1297,20 @@ ip_vs_add_service(struct net *net, struct ip_vs_service_user_kern *u,
static int
ip_vs_edit_service(struct ip_vs_service *svc, struct ip_vs_service_user_kern *u)
{
struct ip_vs_scheduler *sched, *old_sched;
struct ip_vs_scheduler *sched = NULL, *old_sched;
struct ip_vs_pe *pe = NULL, *old_pe = NULL;
int ret = 0;

/*
* Lookup the scheduler, by 'u->sched_name'
*/
sched = ip_vs_scheduler_get(u->sched_name);
if (sched == NULL) {
pr_info("Scheduler module ip_vs_%s not found\n", u->sched_name);
return -ENOENT;
if (strcmp(u->sched_name, "none")) {
sched = ip_vs_scheduler_get(u->sched_name);
if (!sched) {
pr_info("Scheduler module ip_vs_%s not found\n",
u->sched_name);
return -ENOENT;
}
}
old_sched = sched;

Expand Down Expand Up @@ -1329,14 +1338,20 @@ ip_vs_edit_service(struct ip_vs_service *svc, struct ip_vs_service_user_kern *u)

old_sched = rcu_dereference_protected(svc->scheduler, 1);
if (sched != old_sched) {
if (old_sched) {
ip_vs_unbind_scheduler(svc, old_sched);
RCU_INIT_POINTER(svc->scheduler, NULL);
/* Wait all svc->sched_data users */
synchronize_rcu();
}
/* Bind the new scheduler */
ret = ip_vs_bind_scheduler(svc, sched);
if (ret) {
old_sched = sched;
goto out;
if (sched) {
ret = ip_vs_bind_scheduler(svc, sched);
if (ret) {
ip_vs_scheduler_put(sched);
goto out;
}
}
/* Unbind the old scheduler on success */
ip_vs_unbind_scheduler(svc, old_sched);
}

/*
Expand Down Expand Up @@ -1982,6 +1997,7 @@ static int ip_vs_info_seq_show(struct seq_file *seq, void *v)
const struct ip_vs_iter *iter = seq->private;
const struct ip_vs_dest *dest;
struct ip_vs_scheduler *sched = rcu_dereference(svc->scheduler);
char *sched_name = sched ? sched->name : "none";

if (iter->table == ip_vs_svc_table) {
#ifdef CONFIG_IP_VS_IPV6
Expand All @@ -1990,18 +2006,18 @@ static int ip_vs_info_seq_show(struct seq_file *seq, void *v)
ip_vs_proto_name(svc->protocol),
&svc->addr.in6,
ntohs(svc->port),
sched->name);
sched_name);
else
#endif
seq_printf(seq, "%s %08X:%04X %s %s ",
ip_vs_proto_name(svc->protocol),
ntohl(svc->addr.ip),
ntohs(svc->port),
sched->name,
sched_name,
(svc->flags & IP_VS_SVC_F_ONEPACKET)?"ops ":"");
} else {
seq_printf(seq, "FWM %08X %s %s",
svc->fwmark, sched->name,
svc->fwmark, sched_name,
(svc->flags & IP_VS_SVC_F_ONEPACKET)?"ops ":"");
}

Expand Down Expand Up @@ -2427,13 +2443,15 @@ ip_vs_copy_service(struct ip_vs_service_entry *dst, struct ip_vs_service *src)
{
struct ip_vs_scheduler *sched;
struct ip_vs_kstats kstats;
char *sched_name;

sched = rcu_dereference_protected(src->scheduler, 1);
sched_name = sched ? sched->name : "none";
dst->protocol = src->protocol;
dst->addr = src->addr.ip;
dst->port = src->port;
dst->fwmark = src->fwmark;
strlcpy(dst->sched_name, sched->name, sizeof(dst->sched_name));
strlcpy(dst->sched_name, sched_name, sizeof(dst->sched_name));
dst->flags = src->flags;
dst->timeout = src->timeout / HZ;
dst->netmask = src->netmask;
Expand Down Expand Up @@ -2892,6 +2910,7 @@ static int ip_vs_genl_fill_service(struct sk_buff *skb,
struct ip_vs_flags flags = { .flags = svc->flags,
.mask = ~0 };
struct ip_vs_kstats kstats;
char *sched_name;

nl_service = nla_nest_start(skb, IPVS_CMD_ATTR_SERVICE);
if (!nl_service)
Expand All @@ -2910,8 +2929,9 @@ static int ip_vs_genl_fill_service(struct sk_buff *skb,
}

sched = rcu_dereference_protected(svc->scheduler, 1);
sched_name = sched ? sched->name : "none";
pe = rcu_dereference_protected(svc->pe, 1);
if (nla_put_string(skb, IPVS_SVC_ATTR_SCHED_NAME, sched->name) ||
if (nla_put_string(skb, IPVS_SVC_ATTR_SCHED_NAME, sched_name) ||
(pe && nla_put_string(skb, IPVS_SVC_ATTR_PE_NAME, pe->name)) ||
nla_put(skb, IPVS_SVC_ATTR_FLAGS, sizeof(flags), &flags) ||
nla_put_u32(skb, IPVS_SVC_ATTR_TIMEOUT, svc->timeout / HZ) ||
Expand Down
12 changes: 6 additions & 6 deletions net/netfilter/ipvs/ip_vs_sched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ void ip_vs_unbind_scheduler(struct ip_vs_service *svc,

if (sched->done_service)
sched->done_service(svc);
/* svc->scheduler can not be set to NULL */
/* svc->scheduler can be set to NULL only by caller */
}


Expand Down Expand Up @@ -147,21 +147,21 @@ void ip_vs_scheduler_put(struct ip_vs_scheduler *scheduler)

void ip_vs_scheduler_err(struct ip_vs_service *svc, const char *msg)
{
struct ip_vs_scheduler *sched;
struct ip_vs_scheduler *sched = rcu_dereference(svc->scheduler);
char *sched_name = sched ? sched->name : "none";

sched = rcu_dereference(svc->scheduler);
if (svc->fwmark) {
IP_VS_ERR_RL("%s: FWM %u 0x%08X - %s\n",
sched->name, svc->fwmark, svc->fwmark, msg);
sched_name, svc->fwmark, svc->fwmark, msg);
#ifdef CONFIG_IP_VS_IPV6
} else if (svc->af == AF_INET6) {
IP_VS_ERR_RL("%s: %s [%pI6c]:%d - %s\n",
sched->name, ip_vs_proto_name(svc->protocol),
sched_name, ip_vs_proto_name(svc->protocol),
&svc->addr.in6, ntohs(svc->port), msg);
#endif
} else {
IP_VS_ERR_RL("%s: %s %pI4:%d - %s\n",
sched->name, ip_vs_proto_name(svc->protocol),
sched_name, ip_vs_proto_name(svc->protocol),
&svc->addr.ip, ntohs(svc->port), msg);
}
}
Expand Down

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