fib_trie: Make fib_table rcu safe
The fib_table was wrapped in several places with an
rcu_read_lock/rcu_read_unlock however after looking over the code I found
several spots where the tables were being accessed as just standard
pointers without any protections. This change fixes that so that all of
the proper protections are in place when accessing the table to take RCU
replacement or removal of the table into account.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 57be71d..220c4b4 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -89,17 +89,14 @@
switch (id) {
case RT_TABLE_LOCAL:
- net->ipv4.fib_local = tb;
+ rcu_assign_pointer(net->ipv4.fib_local, tb);
break;
-
case RT_TABLE_MAIN:
- net->ipv4.fib_main = tb;
+ rcu_assign_pointer(net->ipv4.fib_main, tb);
break;
-
case RT_TABLE_DEFAULT:
- net->ipv4.fib_default = tb;
+ rcu_assign_pointer(net->ipv4.fib_default, tb);
break;
-
default:
break;
}
@@ -132,13 +129,14 @@
static void fib_flush(struct net *net)
{
int flushed = 0;
- struct fib_table *tb;
- struct hlist_head *head;
unsigned int h;
for (h = 0; h < FIB_TABLE_HASHSZ; h++) {
- head = &net->ipv4.fib_table_hash[h];
- hlist_for_each_entry(tb, head, tb_hlist)
+ struct hlist_head *head = &net->ipv4.fib_table_hash[h];
+ struct hlist_node *tmp;
+ struct fib_table *tb;
+
+ hlist_for_each_entry_safe(tb, tmp, head, tb_hlist)
flushed += fib_table_flush(tb);
}
@@ -665,10 +663,12 @@
s_h = cb->args[0];
s_e = cb->args[1];
+ rcu_read_lock();
+
for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_e = 0) {
e = 0;
head = &net->ipv4.fib_table_hash[h];
- hlist_for_each_entry(tb, head, tb_hlist) {
+ hlist_for_each_entry_rcu(tb, head, tb_hlist) {
if (e < s_e)
goto next;
if (dumped)
@@ -682,6 +682,8 @@
}
}
out:
+ rcu_read_unlock();
+
cb->args[1] = e;
cb->args[0] = h;
@@ -1117,14 +1119,34 @@
rtnl_lock();
for (i = 0; i < FIB_TABLE_HASHSZ; i++) {
- struct fib_table *tb;
- struct hlist_head *head;
+ struct hlist_head *head = &net->ipv4.fib_table_hash[i];
struct hlist_node *tmp;
+ struct fib_table *tb;
- head = &net->ipv4.fib_table_hash[i];
- hlist_for_each_entry_safe(tb, tmp, head, tb_hlist) {
- hlist_del(&tb->tb_hlist);
+ /* this is done in two passes as flushing the table could
+ * cause it to be reallocated in order to accommodate new
+ * tnodes at the root as the table shrinks.
+ */
+ hlist_for_each_entry_safe(tb, tmp, head, tb_hlist)
fib_table_flush(tb);
+
+ hlist_for_each_entry_safe(tb, tmp, head, tb_hlist) {
+#ifdef CONFIG_IP_MULTIPLE_TABLES
+ switch (tb->tb_id) {
+ case RT_TABLE_LOCAL:
+ RCU_INIT_POINTER(net->ipv4.fib_local, NULL);
+ break;
+ case RT_TABLE_MAIN:
+ RCU_INIT_POINTER(net->ipv4.fib_main, NULL);
+ break;
+ case RT_TABLE_DEFAULT:
+ RCU_INIT_POINTER(net->ipv4.fib_default, NULL);
+ break;
+ default:
+ break;
+ }
+#endif
+ hlist_del(&tb->tb_hlist);
fib_free_table(tb);
}
}