net/ipv4: Use proper RCU APIs for writer-side in udp_offload.c
RCU writer side should use rcu_dereference_protected() and not
rcu_dereference(), fix that. This also removes the "suspicious RCU usage"
warning seen when running with CONFIG_PROVE_RCU.
Also, don't use rcu_assign_pointer/rcu_dereference for pointers
which are invisible beyond the udp offload code.
Fixes: b582ef0 ('net: Add GRO support for UDP encapsulating protocols')
Reported-by: Eric Dumazet <edumazet@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 2ffea6f..88b4023 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -17,6 +17,8 @@
static DEFINE_SPINLOCK(udp_offload_lock);
static struct udp_offload_priv __rcu *udp_offload_base __read_mostly;
+#define udp_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&udp_offload_lock))
+
struct udp_offload_priv {
struct udp_offload *offload;
struct rcu_head rcu;
@@ -100,7 +102,6 @@
int udp_add_offload(struct udp_offload *uo)
{
- struct udp_offload_priv __rcu **head = &udp_offload_base;
struct udp_offload_priv *new_offload = kzalloc(sizeof(*new_offload), GFP_ATOMIC);
if (!new_offload)
@@ -109,8 +110,8 @@
new_offload->offload = uo;
spin_lock(&udp_offload_lock);
- rcu_assign_pointer(new_offload->next, rcu_dereference(*head));
- rcu_assign_pointer(*head, new_offload);
+ new_offload->next = udp_offload_base;
+ rcu_assign_pointer(udp_offload_base, new_offload);
spin_unlock(&udp_offload_lock);
return 0;
@@ -130,12 +131,12 @@
spin_lock(&udp_offload_lock);
- uo_priv = rcu_dereference(*head);
+ uo_priv = udp_deref_protected(*head);
for (; uo_priv != NULL;
- uo_priv = rcu_dereference(*head)) {
-
+ uo_priv = udp_deref_protected(*head)) {
if (uo_priv->offload == uo) {
- rcu_assign_pointer(*head, rcu_dereference(uo_priv->next));
+ rcu_assign_pointer(*head,
+ udp_deref_protected(uo_priv->next));
goto unlock;
}
head = &uo_priv->next;
