From e2de6c4048989007b353164b19d6b7d5be4fa9e3 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Tue, 27 Aug 2019 09:51:30 +0100
Subject: rxrpc: Use info in skbuff instead of reparsing a jumbo packet

Use the information now cached in the skbuff private data to avoid the need
to reparse a jumbo packet.  We can find all the subpackets by dead
reckoning, so it's only necessary to note how many there are, whether the
last one is flagged as LAST_PACKET and whether any have the REQUEST_ACK
flag set.

This is necessary as once recvmsg() can see the packet, it can start
modifying it, such as doing in-place decryption.

Fixes: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code")
Signed-off-by: David Howells <dhowells@redhat.com>
---
 net/rxrpc/recvmsg.c | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

(limited to 'net/rxrpc/recvmsg.c')

diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c
index 9a7e1bc9791d..e49eacfaf4d6 100644
--- a/net/rxrpc/recvmsg.c
+++ b/net/rxrpc/recvmsg.c
@@ -177,7 +177,8 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 	struct sk_buff *skb;
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top;
-	u8 flags;
+	bool last = false;
+	u8 subpacket;
 	int ix;
 
 	_enter("%d", call->debug_id);
@@ -191,10 +192,13 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 	skb = call->rxtx_buffer[ix];
 	rxrpc_see_skb(skb, rxrpc_skb_rx_rotated);
 	sp = rxrpc_skb(skb);
-	flags = sp->hdr.flags;
-	serial = sp->hdr.serial;
-	if (call->rxtx_annotations[ix] & RXRPC_RX_ANNO_JUMBO)
-		serial += (call->rxtx_annotations[ix] & RXRPC_RX_ANNO_JUMBO) - 1;
+
+	subpacket = call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
+	serial = sp->hdr.serial + subpacket;
+
+	if (subpacket == sp->nr_subpackets - 1 &&
+	    sp->rx_flags & RXRPC_SKB_INCL_LAST)
+		last = true;
 
 	call->rxtx_buffer[ix] = NULL;
 	call->rxtx_annotations[ix] = 0;
@@ -203,9 +207,8 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 
 	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 
-	_debug("%u,%u,%02x", hard_ack, top, flags);
 	trace_rxrpc_receive(call, rxrpc_receive_rotate, serial, hard_ack);
-	if (flags & RXRPC_LAST_PACKET) {
+	if (last) {
 		rxrpc_end_rx_phase(call, serial);
 	} else {
 		/* Check to see if there's an ACK that needs sending. */
@@ -233,18 +236,19 @@ static int rxrpc_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	rxrpc_seq_t seq = sp->hdr.seq;
 	u16 cksum = sp->hdr.cksum;
+	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;
 
 	_enter("");
 
 	/* For all but the head jumbo subpacket, the security checksum is in a
 	 * jumbo header immediately prior to the data.
 	 */
-	if ((annotation & RXRPC_RX_ANNO_JUMBO) > 1) {
+	if (subpacket > 0) {
 		__be16 tmp;
 		if (skb_copy_bits(skb, offset - 2, &tmp, 2) < 0)
 			BUG();
 		cksum = ntohs(tmp);
-		seq += (annotation & RXRPC_RX_ANNO_JUMBO) - 1;
+		seq += subpacket;
 	}
 
 	return call->conn->security->verify_packet(call, skb, offset, len,
@@ -265,19 +269,18 @@ static int rxrpc_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
 			     u8 *_annotation,
 			     unsigned int *_offset, unsigned int *_len)
 {
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	unsigned int offset = sizeof(struct rxrpc_wire_header);
 	unsigned int len;
 	int ret;
 	u8 annotation = *_annotation;
+	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;
 
 	/* Locate the subpacket */
+	offset += subpacket * RXRPC_JUMBO_SUBPKTLEN;
 	len = skb->len - offset;
-	if ((annotation & RXRPC_RX_ANNO_JUMBO) > 0) {
-		offset += (((annotation & RXRPC_RX_ANNO_JUMBO) - 1) *
-			   RXRPC_JUMBO_SUBPKTLEN);
-		len = (annotation & RXRPC_RX_ANNO_JLAST) ?
-			skb->len - offset : RXRPC_JUMBO_SUBPKTLEN;
-	}
+	if (subpacket < sp->nr_subpackets - 1)
+		len = RXRPC_JUMBO_DATALEN;
 
 	if (!(annotation & RXRPC_RX_ANNO_VERIFIED)) {
 		ret = rxrpc_verify_packet(call, skb, annotation, offset, len);
@@ -303,6 +306,7 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 {
 	struct rxrpc_skb_priv *sp;
 	struct sk_buff *skb;
+	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top, seq;
 	size_t remain;
 	bool last;
@@ -339,9 +343,12 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 		sp = rxrpc_skb(skb);
 
-		if (!(flags & MSG_PEEK))
+		if (!(flags & MSG_PEEK)) {
+			serial = sp->hdr.serial;
+			serial += call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
 			trace_rxrpc_receive(call, rxrpc_receive_front,
-					    sp->hdr.serial, seq);
+					    serial, seq);
+		}
 
 		if (msg)
 			sock_recv_timestamp(msg, sock->sk, skb);
-- 
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