Patrick McHardy wrote:
Chuck Ebbert wrote:
Reported at https://bugzilla.redhat.com/show_bug.cgi?id=449315
In find_appropriate_src():
hlist_for_each_entry_rcu(nat, n, &bysource[h], bysource) {
ct = nat->ct;
if (same_src(ct, tuple)) {
Dereference of ct in same_src() causes the oops. This only seems to
happen on heavily loaded firewall machines. Kernel 2.6.24.7 works.
The reporter identifies commit 4d354c5782dc352cec187845d17eedc2c2bfcf67
("[NETFILTER]: nf_nat: use RCU for bysource hash") as a possible cause
of the problem.
We have a similar looking report, but that one also affects 2.6.24:
http://bugzilla.kernel.org/show_bug.cgi?id=10875
Anyways, does this patch help? When reallocating storage
for a conntrack, it is replaced in the list before assigning
the nat->ct pointer.
I'm afraid we also need this one on top - when reallocating
an extension, we must not free the old storage since it may
still be used in a RCU read side.
diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h
index f736e84..f80c0ed 100644
--- a/include/net/netfilter/nf_conntrack_extend.h
+++ b/include/net/netfilter/nf_conntrack_extend.h
@@ -15,6 +15,7 @@ enum nf_ct_ext_id
/* Extensions: optional stuff which isn't permanently in struct. */
struct nf_ct_ext {
+ struct rcu_head rcu;
u8 offset[NF_CT_EXT_NUM];
u8 len;
char data[0];
diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
index bcc19fa..90d4a74 100644
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -59,12 +59,19 @@ nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
if (!*ext)
return NULL;
+ INIT_RCU_HEAD(&(*ext)->rcu);
(*ext)->offset[id] = off;
(*ext)->len = len;
return (void *)(*ext) + off;
}
+static void __nf_ct_ext_destroy_rcu(struct rcu_head *head)
+{
+ struct nf_ct_ext *ext = container_of(head, struct nf_ct_ext, rcu);
+ kfree(ext);
+}
+
void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
{
struct nf_ct_ext *new;
@@ -106,7 +113,7 @@ void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
(void *)ct->ext + ct->ext->offset[i]);
rcu_read_unlock();
}
- kfree(ct->ext);
+ call_rcu(&ct->ext->rcu, __nf_ct_ext_destroy_rcu);
ct->ext = new;
}
