* Re: netfilter: ctnetlink: deliver events for conntracks changed from userspace
2009-04-06 12:32 netfilter: ctnetlink: deliver events for conntracks changed from userspace Patrick McHardy
@ 2009-04-06 14:39 ` Pablo Neira Ayuso
2009-04-06 14:50 ` Patrick McHardy
0 siblings, 1 reply; 3+ messages in thread
From: Pablo Neira Ayuso @ 2009-04-06 14:39 UTC (permalink / raw)
To: Patrick McHardy; +Cc: Netfilter Development Mailinglist
[-- Attachment #1: Type: text/plain, Size: 2299 bytes --]
Patrick McHardy wrote:
> Pablo, I'm looking at a regression introduced by this patch
> and I'm not sure about the intentions:
>
>> +int nf_ct_expect_related(struct nf_conntrack_expect *expect)
>> +{
>> + int ret;
>> +
>> + spin_lock_bh(&nf_conntrack_lock);
>> + ret = __nf_ct_expect_check(expect);
>> + if (ret < 0)
>> + goto out;
>
> This is unfortunately broken since we return 0 when refreshing an
> existing expectation. This will create an identical expectation
> for each refresh.
Oh sorry.
>> nf_ct_expect_insert(expect);
>> + atomic_inc(&expect->use);
>
> This I don't understand - the caller is holding a reference, why
> do we need another one?
I thought that the expectation timer may expire while delivering the
event, but that cannot happen since we still hold the reference until
the expectation setup is finished (nf_ct_expect_alloc() gets the
refcount, later nf_ct_expect_put() puts it).
>> + spin_unlock_bh(&nf_conntrack_lock);
>> nf_ct_expect_event(IPEXP_NEW, expect);
>> - ret = 0;
>> + nf_ct_expect_put(expect);
>> + return ret;
>> out:
>> spin_unlock_bh(&nf_conntrack_lock);
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(nf_ct_expect_related);
>>
>> +int nf_ct_expect_related_report(struct nf_conntrack_expect *expect,
>> + u32 pid, int report)
>> +{
>> + int ret;
>> +
>> + spin_lock_bh(&nf_conntrack_lock);
>> + ret = __nf_ct_expect_check(expect);
>> + if (ret < 0)
>> + goto out;
>
> Same problem
>
>> + nf_ct_expect_insert(expect);
>> +out:
>> + spin_unlock_bh(&nf_conntrack_lock);
>> + if (ret == 0)
>> + nf_ct_expect_event_report(IPEXP_NEW, expect, pid,
>> report);
>
> But here we don't take the reference, despite having the exact
> same situation.
I don't find an answer for that, likely that I got confused for some
reason, sorry.
> The next question would be - why do we need those two functions at
> all? Aside from the apparently unnecessary reference counting, the
> only difference is reporting, and that actually uses the exact
> same code path.
Is the patch attached on the right track?
--
"Los honestos son inadaptados sociales" -- Les Luthiers
[-- Attachment #2: x.patch --]
[-- Type: text/x-diff, Size: 3298 bytes --]
netfilter: ctnetlink: fix regression in expectation handling
This patch fixes a regression (introduced by myself) that results
in an expectation re-insertion since __nf_ct_expect_check() may
return 0 for expectation timer refreshing.
This patch also removes a unnecessary refcount bump that
prentended to avoid a possible race condition with event delivery
and expectation timers (as said, not needed since we hold a
reference to the object since until we finish the expectation
setup). This also merges nf_ct_expect_related_report() and
nf_ct_expect_related() which look basically the same.
Reported-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
include/net/netfilter/nf_conntrack_expect.h | 5 ++++-
net/netfilter/nf_conntrack_expect.c | 30 +++++----------------------
2 files changed, 10 insertions(+), 25 deletions(-)
diff --git a/include/net/netfilter/nf_conntrack_expect.h b/include/net/netfilter/nf_conntrack_expect.h
index ab17a15..a965280 100644
--- a/include/net/netfilter/nf_conntrack_expect.h
+++ b/include/net/netfilter/nf_conntrack_expect.h
@@ -99,9 +99,12 @@ void nf_ct_expect_init(struct nf_conntrack_expect *, unsigned int, u_int8_t,
const union nf_inet_addr *,
u_int8_t, const __be16 *, const __be16 *);
void nf_ct_expect_put(struct nf_conntrack_expect *exp);
-int nf_ct_expect_related(struct nf_conntrack_expect *expect);
int nf_ct_expect_related_report(struct nf_conntrack_expect *expect,
u32 pid, int report);
+static inline int nf_ct_expect_related(struct nf_conntrack_expect *expect)
+{
+ return nf_ct_expect_related_report(expect, 0, 0);
+}
#endif /*_NF_CONNTRACK_EXPECT_H*/
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index 357ba39..0e2caad 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -372,7 +372,7 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
struct net *net = nf_ct_exp_net(expect);
struct hlist_node *n;
unsigned int h;
- int ret = 0;
+ int ret = 1;
if (!master_help->helper) {
ret = -ESHUTDOWN;
@@ -412,41 +412,23 @@ out:
return ret;
}
-int nf_ct_expect_related(struct nf_conntrack_expect *expect)
+int nf_ct_expect_related_report(struct nf_conntrack_expect *expect,
+ u32 pid, int report)
{
int ret;
spin_lock_bh(&nf_conntrack_lock);
ret = __nf_ct_expect_check(expect);
- if (ret < 0)
+ if (ret <= 0)
goto out;
+ ret = 0;
nf_ct_expect_insert(expect);
- atomic_inc(&expect->use);
- spin_unlock_bh(&nf_conntrack_lock);
- nf_ct_expect_event(IPEXP_NEW, expect);
- nf_ct_expect_put(expect);
- return ret;
-out:
spin_unlock_bh(&nf_conntrack_lock);
+ nf_ct_expect_event_report(IPEXP_NEW, expect, pid, report);
return ret;
-}
-EXPORT_SYMBOL_GPL(nf_ct_expect_related);
-
-int nf_ct_expect_related_report(struct nf_conntrack_expect *expect,
- u32 pid, int report)
-{
- int ret;
-
- spin_lock_bh(&nf_conntrack_lock);
- ret = __nf_ct_expect_check(expect);
- if (ret < 0)
- goto out;
- nf_ct_expect_insert(expect);
out:
spin_unlock_bh(&nf_conntrack_lock);
- if (ret == 0)
- nf_ct_expect_event_report(IPEXP_NEW, expect, pid, report);
return ret;
}
EXPORT_SYMBOL_GPL(nf_ct_expect_related_report);
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