[PATCH v2 bpf/net 4/6] sockmap: Pass gfp_t flag to sk_psock_skb_ingress().

[Kuniyuki Iwashima <kuniyu@google.com>]

SOCKMAP memory accounting for UDP is broken for two reasons:

  1. sk->sk_forward_alloc must be changed under
     spin_lock_bh(&sk->sk_receive_queue.lock)

  2. sk_psock_skb_ingress_self() should not be used for UDP
     since UDP may reclaim sk->sk_forward_alloc partially
     before passing skb to sockmap, resulting in a negative
     sk->sk_forward_alloc

This is a prep commit to consolidate sk_psock_skb_ingress_self()
and centralise the fix to sk_psock_skb_ingress().

Let's pass gfp_t flag to sk_psock_skb_ingress() and inline
sk_psock_create_ingress_msg().

Note that now alloc_sk_msg() is called first.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/core/skmsg.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 3d7eb2f4ac98..57845b0d8a71 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -529,18 +529,6 @@ static struct sk_msg *alloc_sk_msg(gfp_t gfp)
 	return msg;
 }
 
-static struct sk_msg *sk_psock_create_ingress_msg(struct sock *sk,
-						  struct sk_buff *skb)
-{
-	if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
-		return NULL;
-
-	if (!sk_rmem_schedule(sk, skb, skb->truesize))
-		return NULL;
-
-	return alloc_sk_msg(GFP_KERNEL);
-}
-
 static int sk_psock_skb_ingress_enqueue(struct sk_buff *skb,
 					u32 off, u32 len,
 					struct sk_psock *psock,
@@ -588,11 +576,11 @@ static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb
 				     u32 off, u32 len, bool take_ref);
 
 static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb,
-				u32 off, u32 len)
+				u32 off, u32 len, gfp_t gfp_flags)
 {
 	struct sock *sk = psock->sk;
 	struct sk_msg *msg;
-	int err;
+	int err = -EAGAIN;
 
 	/* If we are receiving on the same sock skb->sk is already assigned,
 	 * skip memory accounting and owner transition seeing it already set
@@ -600,9 +588,16 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb,
 	 */
 	if (unlikely(skb->sk == sk))
 		return sk_psock_skb_ingress_self(psock, skb, off, len, true);
-	msg = sk_psock_create_ingress_msg(sk, skb);
+
+	msg = alloc_sk_msg(gfp_flags);
 	if (!msg)
-		return -EAGAIN;
+		goto out;
+
+	if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
+		goto free;
+
+	if (!sk_rmem_schedule(sk, skb, skb->truesize))
+		goto free;
 
 	/* This will transition ownership of the data from the socket where
 	 * the BPF program was run initiating the redirect to the socket
@@ -613,8 +608,12 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb,
 	skb_set_owner_r(skb, sk);
 	err = sk_psock_skb_ingress_enqueue(skb, off, len, psock, sk, msg, true);
 	if (err < 0)
-		kfree(msg);
+		goto free;
+out:
 	return err;
+free:
+	kfree(msg);
+	goto out;
 }
 
 /* Puts an skb on the ingress queue of the socket already assigned to the
@@ -652,7 +651,7 @@ static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
 		return skb_send_sock(psock->sk, skb, off, len);
 	}
 
-	return sk_psock_skb_ingress(psock, skb, off, len);
+	return sk_psock_skb_ingress(psock, skb, off, len, GFP_KERNEL);
 }
 
 static void sk_psock_skb_state(struct sk_psock *psock,
-- 
2.53.0.310.g728cabbaf7-goog