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Commit a664a4f7 authored by Shlomo Pongratz's avatar Shlomo Pongratz Committed by David S. Miller
Browse files

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: b582ef09 ('net: Add GRO support for UDP encapsulating protocols')
Reported-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: default avatarOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: default avatarShlomo Pongratz <shlomop@mellanox.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9330ed16

net/ipv4/udp_offload.c

+8 −7
Original line number Diff line number Diff line
@@ -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 @@ out: 


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 @@ int udp_add_offload(struct udp_offload *uo) 
	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 @@ void udp_del_offload(struct udp_offload *uo) 


	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;