Re: [Patch net] ipt_CLUSTERIP: fix a refcount bug in clusterip_config_find_get()

[Cong Wang]

On Thu, Feb 8, 2018 at 12:01 AM, Florian Westphal  wrote:
> Cong Wang  wrote:
>> In clusterip_config_find_get() we hold RCU read lock so it could
>> run concurrently with clusterip_config_entry_put(), as a result,
>> the refcnt could go back to 1 from 0, which leads to a double
>> list_del()... Just replace refcount_inc() with
>> refcount_inc_not_zero(), as for c->refcount.
>>
>> Fixes: d73f33b16883 ("netfilter: CLUSTERIP: RCU conversion")
>> Cc: Eric Dumazet 
>> Cc: Pablo Neira Ayuso 
>> Signed-off-by: Cong Wang 
>> ---
>>  net/ipv4/netfilter/ipt_CLUSTERIP.c | 6 --
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c 
>> b/net/ipv4/netfilter/ipt_CLUSTERIP.c
>> index 1ff72b87a066..4537b1686c7c 100644
>> --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
>> +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
>> @@ -154,8 +154,10 @@ clusterip_config_find_get(struct net *net, __be32 
>> clusterip, int entry)
>>  #endif
>>   if (unlikely(!refcount_inc_not_zero(>refcount)))
>>   c = NULL;
>> - else if (entry)
>> - refcount_inc(>entries);
>> + else if (entry) {
>> + if (unlikely(!refcount_inc_not_zero(>entries)))
>
> this needs to call clusterip_config_put(c); too, else we leak one
> reference.
>
> Other than that this looks good.

Right, good catch! I will send v2.

Re: [Patch net] ipt_CLUSTERIP: fix a refcount bug in clusterip_config_find_get()

[Florian Westphal]

Cong Wang  wrote:
> In clusterip_config_find_get() we hold RCU read lock so it could
> run concurrently with clusterip_config_entry_put(), as a result,
> the refcnt could go back to 1 from 0, which leads to a double
> list_del()... Just replace refcount_inc() with
> refcount_inc_not_zero(), as for c->refcount.
> 
> Fixes: d73f33b16883 ("netfilter: CLUSTERIP: RCU conversion")
> Cc: Eric Dumazet 
> Cc: Pablo Neira Ayuso 
> Signed-off-by: Cong Wang 
> ---
>  net/ipv4/netfilter/ipt_CLUSTERIP.c | 6 --
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c 
> b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> index 1ff72b87a066..4537b1686c7c 100644
> --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
> +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> @@ -154,8 +154,10 @@ clusterip_config_find_get(struct net *net, __be32 
> clusterip, int entry)
>  #endif
>   if (unlikely(!refcount_inc_not_zero(>refcount)))
>   c = NULL;
> - else if (entry)
> - refcount_inc(>entries);
> + else if (entry) {
> + if (unlikely(!refcount_inc_not_zero(>entries)))

this needs to call clusterip_config_put(c); too, else we leak one
reference.

Other than that this looks good.

[Patch net] ipt_CLUSTERIP: fix a refcount bug in clusterip_config_find_get()

[Cong Wang]

In clusterip_config_find_get() we hold RCU read lock so it could
run concurrently with clusterip_config_entry_put(), as a result,
the refcnt could go back to 1 from 0, which leads to a double
list_del()... Just replace refcount_inc() with
refcount_inc_not_zero(), as for c->refcount.

Fixes: d73f33b16883 ("netfilter: CLUSTERIP: RCU conversion")
Cc: Eric Dumazet 
Cc: Pablo Neira Ayuso 
Signed-off-by: Cong Wang 
---
 net/ipv4/netfilter/ipt_CLUSTERIP.c | 6 --
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c 
b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 1ff72b87a066..4537b1686c7c 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -154,8 +154,10 @@ clusterip_config_find_get(struct net *net, __be32 
clusterip, int entry)
 #endif
if (unlikely(!refcount_inc_not_zero(>refcount)))
c = NULL;
-   else if (entry)
-   refcount_inc(>entries);
+   else if (entry) {
+   if (unlikely(!refcount_inc_not_zero(>entries)))
+   c = NULL;
+   }
}
rcu_read_unlock_bh();
 
-- 
2.13.0