sctp: implement memory accounting on tx path

Now when sending packets, sk_mem_charge() and sk_mem_uncharge() have been
used to set sk_forward_alloc. We just need to call sk_wmem_schedule() to
check if the allocated should be raised, and call sk_mem_reclaim() to
check if the allocated should be reduced when it's under memory pressure.

If sk_wmem_schedule() returns false, which means no memory is allowed to
allocate, it will block and wait for memory to become available.

Note different from tcp, sctp wait_for_buf happens before allocating any
skb, so memory accounting check is done with the whole msg_len before it
too.

Reported-by: Matteo Croce <[email protected]>
Tested-by: Matteo Croce <[email protected]>
Acked-by: Neil Horman <[email protected]>
Acked-by: Marcelo Ricardo Leitner <[email protected]>
Signed-off-by: Xin Long <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
(cherry picked from commit 1033990)

Orabug: 31753070
CVE: CVE-2019-3874

Signed-off-by: Saeed Mirzamohammadi <[email protected]>
Reviewed-by: John Donnelly  <[email protected]>

Conflicts:
	net/sctp/socket.c - modified to match the UEK code base.
Signed-off-by: Somasundaram Krishnasamy <[email protected]>

Author: lxin

net/sctp/socket.c

@@ -1981,9 +1981,11 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len)
 	if (sctp_wspace(asoc) < msg_len)
 		sctp_prsctp_prune(asoc, sinfo, msg_len - sctp_wspace(asoc));
 
-	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
-	if (!sctp_wspace(asoc)) {
-		/* sk can be changed by peel off when waiting for buf. */
+	if (sk_under_memory_pressure(sk))
+		sk_mem_reclaim(sk);
+
+	if (sctp_wspace(asoc) <= 0 || !sk_wmem_schedule(sk, msg_len)) {
+		timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
 		err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len);
 		if (err) {
 			if (err == -ESRCH) {
@@ -7894,7 +7896,10 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
 			goto do_error;
 		if (signal_pending(current))
 			goto do_interrupted;
-		if (msg_len <= sctp_wspace(asoc))
+		if (sk_under_memory_pressure(sk))
+			sk_mem_reclaim(sk);
+		if ((int)msg_len <= sctp_wspace(asoc) &&
+		    sk_wmem_schedule(sk, msg_len))
 			break;
 
 		/* Let another process have a go.  Since we are going