bpf, sockmap: Fix potential memory leak on unlikely error case

If skb_linearize is needed and fails we could leak a msg on the error
handling. To fix ensure we kfree the msg block before returning error.
Found during code review.

Fixes: 4363023d2668e ("bpf, sockmap: Avoid failures from skb_to_sgvec when skb has frag_list")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Link: https://lore.kernel.org/bpf/20210712195546.423990-2-john.fastabend@gmail.com

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 9b6160a..15d7128 100644 (file)
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -508,10 +508,8 @@ static int sk_psock_skb_ingress_enqueue(struct sk_buff *skb,
        if (skb_linearize(skb))
                return -EAGAIN;
        num_sge = skb_to_sgvec(skb, msg->sg.data, 0, skb->len);
-       if (unlikely(num_sge < 0)) {
-               kfree(msg);
+       if (unlikely(num_sge < 0))
                return num_sge;
-       }
 
        copied = skb->len;
        msg->sg.start = 0;
@@ -530,6 +528,7 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
 {
        struct sock *sk = psock->sk;
        struct sk_msg *msg;
+       int err;
 
        /* If we are receiving on the same sock skb->sk is already assigned,
         * skip memory accounting and owner transition seeing it already set
@@ -548,7 +547,10 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
         * into user buffers.
         */
        skb_set_owner_r(skb, sk);
-       return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+       err = sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+       if (err < 0)
+               kfree(msg);
+       return err;
 }
 
 /* Puts an skb on the ingress queue of the socket already assigned to the
@@ -559,12 +561,16 @@ static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb
 {
        struct sk_msg *msg = kzalloc(sizeof(*msg), __GFP_NOWARN | GFP_ATOMIC);
        struct sock *sk = psock->sk;
+       int err;
 
        if (unlikely(!msg))
                return -EAGAIN;
        sk_msg_init(msg);
        skb_set_owner_r(skb, sk);
-       return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+       err = sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+       if (err < 0)
+               kfree(msg);
+       return err;
 }
 
 static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,