rxrpc: Fix data-race warning and potential load/store tearing

Fix the following:

        BUG: KCSAN: data-race in rxrpc_peer_keepalive_worker / rxrpc_send_data_packet

which is reporting an issue with the reads and writes to ->last_tx_at in:

        conn->peer->last_tx_at = ktime_get_seconds();

and:

        keepalive_at = peer->last_tx_at + RXRPC_KEEPALIVE_TIME;

The lockless accesses to these to values aren't actually a problem as the
read only needs an approximate time of last transmission for the purposes
of deciding whether or not the transmission of a keepalive packet is
warranted yet.

Also, as ->last_tx_at is a 64-bit value, tearing can occur on a 32-bit
arch.

Fix both of these by switching to an unsigned int for ->last_tx_at and only
storing the LSW of the time64_t.  It can then be reconstructed at need
provided no more than 68 years has elapsed since the last transmission.

Fixes: ace45bec6d77 ("rxrpc: Fix firewall route keepalive")
Reported-by: syzbot+6182afad5045e6703b3d@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/695e7cfb.050a0220.1c677c.036b.GAE@google.com/
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/1107124.1768903985@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 7 insertions, 7 deletions

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 8b5903b6e481..d70db367e358 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -275,7 +275,7 @@ static void rxrpc_send_ack_packet(struct rxrpc_call *call, int nr_kv, size_t len
 	rxrpc_local_dont_fragment(conn->local, why == rxrpc_propose_ack_ping_for_mtu_probe);
 
 	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
-	call->peer->last_tx_at = ktime_get_seconds();
+	rxrpc_peer_mark_tx(call->peer);
 	if (ret < 0) {
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_ack);
@@ -411,7 +411,7 @@ int rxrpc_send_abort_packet(struct rxrpc_call *call)
 
 	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, sizeof(pkt));
 	ret = do_udp_sendmsg(conn->local->socket, &msg, sizeof(pkt));
-	conn->peer->last_tx_at = ktime_get_seconds();
+	rxrpc_peer_mark_tx(conn->peer);
 	if (ret < 0)
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_abort);
@@ -698,7 +698,7 @@ void rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_send_data_req
 			ret = 0;
 			trace_rxrpc_tx_data(call, txb->seq, txb->serial, txb->flags,
 					    rxrpc_txdata_inject_loss);
-			conn->peer->last_tx_at = ktime_get_seconds();
+			rxrpc_peer_mark_tx(conn->peer);
 			goto done;
 		}
 	}
@@ -711,7 +711,7 @@ void rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_send_data_req
 	 */
 	rxrpc_inc_stat(call->rxnet, stat_tx_data_send);
 	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
-	conn->peer->last_tx_at = ktime_get_seconds();
+	rxrpc_peer_mark_tx(conn->peer);
 
 	if (ret == -EMSGSIZE) {
 		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_msgsize);
@@ -797,7 +797,7 @@ void rxrpc_send_conn_abort(struct rxrpc_connection *conn)
 
 	trace_rxrpc_tx_packet(conn->debug_id, &whdr, rxrpc_tx_point_conn_abort);
 
-	conn->peer->last_tx_at = ktime_get_seconds();
+	rxrpc_peer_mark_tx(conn->peer);
 }
 
 /*
@@ -917,7 +917,7 @@ void rxrpc_send_keepalive(struct rxrpc_peer *peer)
 		trace_rxrpc_tx_packet(peer->debug_id, &whdr,
 				      rxrpc_tx_point_version_keepalive);
 
-	peer->last_tx_at = ktime_get_seconds();
+	rxrpc_peer_mark_tx(peer);
 	_leave("");
 }
 
@@ -973,7 +973,7 @@ void rxrpc_send_response(struct rxrpc_connection *conn, struct sk_buff *response
 	if (ret < 0)
 		goto fail;
 
-	conn->peer->last_tx_at = ktime_get_seconds();
+	rxrpc_peer_mark_tx(conn->peer);
 	return;
 
 fail: