netfilter: conntrack: handle initial extension alloc via krealloc

krealloc(NULL, ..) is same as kmalloc(), so we can avoid special-casing
the initial allocation after the prealloc removal (we had to use
->alloc_len as the initial allocation size).

This also means we do not zero the preallocated memory anymore; only
offsets[].  Existing code makes sure the new (used) extension space gets
zeroed out.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
index 5c66816eb965129cc0bc8dcfe76d5fbc9351142e..68ae1be08ed8cf00e553ded7b34b561a95be676b 100644 (file)
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -44,49 +44,24 @@ void __nf_ct_ext_destroy(struct nf_conn *ct)
 }
 EXPORT_SYMBOL(__nf_ct_ext_destroy);
 
-static void *
-nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
-{
-       unsigned int off, len, alloc;
-       struct nf_ct_ext_type *t;
-
-       rcu_read_lock();
-       t = rcu_dereference(nf_ct_ext_types[id]);
-       if (!t) {
-               rcu_read_unlock();
-               return NULL;
-       }
-
-       off = ALIGN(sizeof(struct nf_ct_ext), t->align);
-       len = off + t->len;
-       rcu_read_unlock();
-
-       alloc = max(len, NF_CT_EXT_PREALLOC);
-       *ext = kzalloc(alloc, gfp);
-       if (!*ext)
-               return NULL;
-
-       (*ext)->offset[id] = off;
-       (*ext)->len = len;
-
-       return (void *)(*ext) + off;
-}
-
 void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
 {
+       unsigned int newlen, newoff, oldlen, alloc;
        struct nf_ct_ext *old, *new;
-       int newlen, newoff;
        struct nf_ct_ext_type *t;
 
        /* Conntrack must not be confirmed to avoid races on reallocation. */
        NF_CT_ASSERT(!nf_ct_is_confirmed(ct));
 
        old = ct->ext;
-       if (!old)
-               return nf_ct_ext_create(&ct->ext, id, gfp);
 
-       if (__nf_ct_ext_exist(old, id))
-               return NULL;
+       if (old) {
+               if (__nf_ct_ext_exist(old, id))
+                       return NULL;
+               oldlen = old->len;
+       } else {
+               oldlen = sizeof(*new);
+       }
 
        rcu_read_lock();
        t = rcu_dereference(nf_ct_ext_types[id]);
@@ -95,15 +70,19 @@ void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
                return NULL;
        }
 
-       newoff = ALIGN(old->len, t->align);
+       newoff = ALIGN(oldlen, t->align);
        newlen = newoff + t->len;
        rcu_read_unlock();
 
-       new = __krealloc(old, newlen, gfp);
+       alloc = max(newlen, NF_CT_EXT_PREALLOC);
+       new = __krealloc(old, alloc, gfp);
        if (!new)
                return NULL;
 
-       if (new != old) {
+       if (!old) {
+               memset(new->offset, 0, sizeof(new->offset));
+               ct->ext = new;
+       } else if (new != old) {
                kfree_rcu(old, rcu);
                rcu_assign_pointer(ct->ext, new);
        }