[FIB]: Fix rcu_dereference() abuses in fib_trie.c
node_parent() and tnode_get_child() currently use rcu_dereference().
These functions are called from both
- readers only paths (where rcu_dereference() is needed), and
- writer path (where rcu_dereference() is not needed)
To make explicit where rcu_dereference() is really needed, I
introduced new node_parent_rcu() and tnode_get_child_rcu() functions
which use rcu_dereference(), while node_parent() and tnode_get_child()
dont use it.
Then I changed calling sites where rcu_dereference() was really needed
to call the _rcu() variants.
This should have no impact but for alpha architecture, and may help
future sparse checks.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index fbc80d1..a52334d 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -165,9 +165,13 @@
static inline struct tnode *node_parent(struct node *node)
{
- struct tnode *ret;
+ return (struct tnode *)(node->parent & ~NODE_TYPE_MASK);
+}
- ret = (struct tnode *)(node->parent & ~NODE_TYPE_MASK);
+static inline struct tnode *node_parent_rcu(struct node *node)
+{
+ struct tnode *ret = node_parent(node);
+
return rcu_dereference(ret);
}
@@ -177,13 +181,18 @@
(unsigned long)ptr | NODE_TYPE(node));
}
-/* rcu_read_lock needs to be hold by caller from readside */
-
-static inline struct node *tnode_get_child(struct tnode *tn, int i)
+static inline struct node *tnode_get_child(struct tnode *tn, unsigned int i)
{
- BUG_ON(i >= 1 << tn->bits);
+ BUG_ON(i >= 1U << tn->bits);
- return rcu_dereference(tn->child[i]);
+ return tn->child[i];
+}
+
+static inline struct node *tnode_get_child_rcu(struct tnode *tn, unsigned int i)
+{
+ struct node *ret = tnode_get_child(tn, i);
+
+ return rcu_dereference(ret);
}
static inline int tnode_child_length(const struct tnode *tn)
@@ -938,7 +947,7 @@
if (tkey_sub_equals(tn->key, pos, tn->pos-pos, key)) {
pos = tn->pos + tn->bits;
- n = tnode_get_child(tn, tkey_extract_bits(key, tn->pos, tn->bits));
+ n = tnode_get_child_rcu(tn, tkey_extract_bits(key, tn->pos, tn->bits));
} else
break;
}
@@ -1688,7 +1697,7 @@
p = (struct tnode*) trie; /* Start */
} else
- p = node_parent(c);
+ p = node_parent_rcu(c);
while (p) {
int pos, last;
@@ -1725,7 +1734,7 @@
up:
/* No more children go up one step */
c = (struct node *) p;
- p = node_parent(c);
+ p = node_parent_rcu(c);
}
return NULL; /* Ready. Root of trie */
}
@@ -1987,7 +1996,7 @@
iter->tnode, iter->index, iter->depth);
rescan:
while (cindex < (1<<tn->bits)) {
- struct node *n = tnode_get_child(tn, cindex);
+ struct node *n = tnode_get_child_rcu(tn, cindex);
if (n) {
if (IS_LEAF(n)) {
@@ -2006,7 +2015,7 @@
}
/* Current node exhausted, pop back up */
- p = node_parent((struct node *)tn);
+ p = node_parent_rcu((struct node *)tn);
if (p) {
cindex = tkey_extract_bits(tn->key, p->pos, p->bits)+1;
tn = p;
@@ -2315,7 +2324,7 @@
if (v == SEQ_START_TOKEN)
return 0;
- if (!node_parent(n)) {
+ if (!node_parent_rcu(n)) {
if (iter->trie == iter->trie_local)
seq_puts(seq, "<local>:\n");
else