bpf, sockmap: Fix memleak on ingress msg enqueue

If backlog handler is running during a tear down operation we may enqueue
data on the ingress msg queue while tear down is trying to free it.

 sk_psock_backlog()
   sk_psock_handle_skb()
     skb_psock_skb_ingress()
       sk_psock_skb_ingress_enqueue()
         sk_psock_queue_msg(psock,msg)
                                           spin_lock(ingress_lock)
                                            sk_psock_zap_ingress()
                                             _sk_psock_purge_ingerss_msg()
                                              _sk_psock_purge_ingress_msg()
                                            -- free ingress_msg list --
                                           spin_unlock(ingress_lock)
           spin_lock(ingress_lock)
           list_add_tail(msg,ingress_msg) <- entry on list with no one
                                             left to free it.
           spin_unlock(ingress_lock)

To fix we only enqueue from backlog if the ENABLED bit is set. The tear
down logic clears the bit with ingress_lock set so we wont enqueue the
msg in the last step.

Fixes: 799aa7f98d53 ("skmsg: Avoid lock_sock() in sk_psock_backlog()")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210727160500.1713554-4-john.fastabend@gmail.com

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 96f3190..14ab0c0 100644 (file)
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -285,11 +285,45 @@ static inline struct sk_psock *sk_psock(const struct sock *sk)
        return rcu_dereference_sk_user_data(sk);
 }
 
+static inline void sk_psock_set_state(struct sk_psock *psock,
+                                     enum sk_psock_state_bits bit)
+{
+       set_bit(bit, &psock->state);
+}
+
+static inline void sk_psock_clear_state(struct sk_psock *psock,
+                                       enum sk_psock_state_bits bit)
+{
+       clear_bit(bit, &psock->state);
+}
+
+static inline bool sk_psock_test_state(const struct sk_psock *psock,
+                                      enum sk_psock_state_bits bit)
+{
+       return test_bit(bit, &psock->state);
+}
+
+static inline void sock_drop(struct sock *sk, struct sk_buff *skb)
+{
+       sk_drops_add(sk, skb);
+       kfree_skb(skb);
+}
+
+static inline void drop_sk_msg(struct sk_psock *psock, struct sk_msg *msg)
+{
+       if (msg->skb)
+               sock_drop(psock->sk, msg->skb);
+       kfree(msg);
+}
+
 static inline void sk_psock_queue_msg(struct sk_psock *psock,
                                      struct sk_msg *msg)
 {
        spin_lock_bh(&psock->ingress_lock);
-       list_add_tail(&msg->list, &psock->ingress_msg);
+       if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED))
+               list_add_tail(&msg->list, &psock->ingress_msg);
+       else
+               drop_sk_msg(psock, msg);
        spin_unlock_bh(&psock->ingress_lock);
 }
 
@@ -406,24 +440,6 @@ static inline void sk_psock_restore_proto(struct sock *sk,
                psock->psock_update_sk_prot(sk, psock, true);
 }
 
-static inline void sk_psock_set_state(struct sk_psock *psock,
-                                     enum sk_psock_state_bits bit)
-{
-       set_bit(bit, &psock->state);
-}
-
-static inline void sk_psock_clear_state(struct sk_psock *psock,
-                                       enum sk_psock_state_bits bit)
-{
-       clear_bit(bit, &psock->state);
-}
-
-static inline bool sk_psock_test_state(const struct sk_psock *psock,
-                                      enum sk_psock_state_bits bit)
-{
-       return test_bit(bit, &psock->state);
-}
-
 static inline struct sk_psock *sk_psock_get(struct sock *sk)
 {
        struct sk_psock *psock;

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 036cdb3..2d6249b 100644 (file)
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -584,12 +584,6 @@ static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
        return sk_psock_skb_ingress(psock, skb);
 }
 
-static void sock_drop(struct sock *sk, struct sk_buff *skb)
-{
-       sk_drops_add(sk, skb);
-       kfree_skb(skb);
-}
-
 static void sk_psock_skb_state(struct sk_psock *psock,
                               struct sk_psock_work_state *state,
                               struct sk_buff *skb,