Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Daniel Borkmann says:

====================
bpf-next 2018-11-30

The following pull-request contains BPF updates for your *net-next* tree.

(Getting out bit earlier this time to pull in a dependency from bpf.)

The main changes are:

1) Add libbpf ABI versioning and document API naming conventions
   as well as ABI versioning process, from Andrey.

2) Add a new sk_msg_pop_data() helper for sk_msg based BPF
   programs that is used in conjunction with sk_msg_push_data()
   for adding / removing meta data to the msg data, from John.

3) Optimize convert_bpf_ld_abs() for 0 offset and fix various
   lib and testsuite build failures on 32 bit, from David.

4) Make BPF prog dump for !JIT identical to how we dump subprogs
   when JIT is in use, from Yonghong.

5) Rename btf_get_from_id() to make it more conform with libbpf
   API naming conventions, from Martin.

6) Add a missing BPF kselftest config item, from Naresh.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_bpf.c

@@ -289,12 +289,23 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 {
 	bool cork = false, enospc = msg->sg.start == msg->sg.end;
 	struct sock *sk_redir;
-	u32 tosend;
+	u32 tosend, delta = 0;
 	int ret;
 
 more_data:
-	if (psock->eval == __SK_NONE)
+	if (psock->eval == __SK_NONE) {
+		/* Track delta in msg size to add/subtract it on SK_DROP from
+		 * returned to user copied size. This ensures user doesn't
+		 * get a positive return code with msg_cut_data and SK_DROP
+		 * verdict.
+		 */
+		delta = msg->sg.size;
 		psock->eval = sk_psock_msg_verdict(sk, psock, msg);
+		if (msg->sg.size < delta)
+			delta -= msg->sg.size;
+		else
+			delta = 0;
+	}
 
 	if (msg->cork_bytes &&
 	    msg->cork_bytes > msg->sg.size && !enospc) {
@@ -350,7 +361,7 @@ more_data:
 	default:
 		sk_msg_free_partial(sk, msg, tosend);
 		sk_msg_apply_bytes(psock, tosend);
-		*copied -= tosend;
+		*copied -= (tosend + delta);
 		return -EACCES;
 	}