timers: ensure safe timer removal

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 17 insertions, 12 deletions

diff --git a/src/timers.c b/src/timers.c
index ef30005..42e188c 100644
--- a/src/timers.c
+++ b/src/timers.c
@@ -25,13 +25,18 @@ static inline unsigned long slack_time(unsigned long time)
 	if (unlikely(!peer)) \
 		return;
 
+static inline bool timers_active(struct wireguard_peer *peer)
+{
+	return netif_running(peer->device->dev) && !list_empty(&peer->peer_list);
+}
+
 static void expired_retransmit_handshake(unsigned long ptr)
 {
 	peer_get_from_ptr(ptr);
 	if (peer->timer_handshake_attempts > MAX_TIMER_HANDSHAKES) {
 		pr_debug("%s: Handshake for peer %Lu (%pISpfsc) did not complete after %d attempts, giving up\n", peer->device->dev->name, peer->internal_id, &peer->endpoint.addr, MAX_TIMER_HANDSHAKES + 2);
 
-		if (likely(netif_running(peer->device->dev)))
+		if (likely(timers_active(peer)))
 			del_timer(&peer->timer_send_keepalive);
 		/* We drop all packets without a keypair and don't try again,
 		 * if we try unsuccessfully for too long to make a handshake. */
@@ -39,7 +44,7 @@ static void expired_retransmit_handshake(unsigned long ptr)
 
 		/* We set a timer for destroying any residue that might be left
 		 * of a partial exchange. */
-		if (likely(netif_running(peer->device->dev)) && !timer_pending(&peer->timer_zero_key_material))
+		if (likely(timers_active(peer)) && !timer_pending(&peer->timer_zero_key_material))
 			mod_timer(&peer->timer_zero_key_material, jiffies + (REJECT_AFTER_TIME * 3));
 	} else {
 		++peer->timer_handshake_attempts;
@@ -59,7 +64,7 @@ static void expired_send_keepalive(unsigned long ptr)
 	packet_send_keepalive(peer);
 	if (peer->timer_need_another_keepalive) {
 		peer->timer_need_another_keepalive = false;
-		if (likely(netif_running(peer->device->dev)))
+		if (likely(timers_active(peer)))
 			mod_timer(&peer->timer_send_keepalive, jiffies + KEEPALIVE_TIMEOUT);
 	}
 	peer_put(peer);
@@ -94,7 +99,7 @@ static void expired_send_persistent_keepalive(unsigned long ptr)
 {
 	peer_get_from_ptr(ptr);
 	if (likely(peer->persistent_keepalive_interval)) {
-		if (likely(netif_running(peer->device->dev)))
+		if (likely(timers_active(peer)))
 			del_timer(&peer->timer_send_keepalive);
 		packet_send_keepalive(peer);
 	}
@@ -104,17 +109,17 @@ static void expired_send_persistent_keepalive(unsigned long ptr)
 /* Should be called after an authenticated data packet is sent. */
 void timers_data_sent(struct wireguard_peer *peer)
 {
-	if (likely(netif_running(peer->device->dev)))
+	if (likely(timers_active(peer)))
 		del_timer(&peer->timer_send_keepalive);
 
-	if (likely(netif_running(peer->device->dev)) && !timer_pending(&peer->timer_new_handshake))
+	if (likely(timers_active(peer)) && !timer_pending(&peer->timer_new_handshake))
 		mod_timer(&peer->timer_new_handshake, jiffies + KEEPALIVE_TIMEOUT + REKEY_TIMEOUT);
 }
 
 /* Should be called after an authenticated data packet is received. */
 void timers_data_received(struct wireguard_peer *peer)
 {
-	if (likely(netif_running(peer->device->dev)) && !timer_pending(&peer->timer_send_keepalive))
+	if (likely(timers_active(peer)) && !timer_pending(&peer->timer_send_keepalive))
 		mod_timer(&peer->timer_send_keepalive, jiffies + KEEPALIVE_TIMEOUT);
 	else
 		peer->timer_need_another_keepalive = true;
@@ -123,14 +128,14 @@ void timers_data_received(struct wireguard_peer *peer)
 /* Should be called after any type of authenticated packet is received -- keepalive or data. */
 void timers_any_authenticated_packet_received(struct wireguard_peer *peer)
 {
-	if (likely(netif_running(peer->device->dev)))
+	if (likely(timers_active(peer)))
 		del_timer(&peer->timer_new_handshake);
 }
 
 /* Should be called after a handshake initiation message is sent. */
 void timers_handshake_initiated(struct wireguard_peer *peer)
 {
-	if (likely(netif_running(peer->device->dev))) {
+	if (likely(timers_active(peer))) {
 		del_timer(&peer->timer_send_keepalive);
 		mod_timer(&peer->timer_retransmit_handshake, slack_time(jiffies + REKEY_TIMEOUT + prandom_u32_max(REKEY_TIMEOUT_JITTER_MAX)));
 	}
@@ -139,7 +144,7 @@ void timers_handshake_initiated(struct wireguard_peer *peer)
 /* Should be called after a handshake response message is received and processed or when getting key confirmation via the first data message. */
 void timers_handshake_complete(struct wireguard_peer *peer)
 {
-	if (likely(netif_running(peer->device->dev)))
+	if (likely(timers_active(peer)))
 		del_timer(&peer->timer_retransmit_handshake);
 	peer->timer_handshake_attempts = 0;
 	peer->sent_lastminute_handshake = false;
@@ -149,14 +154,14 @@ void timers_handshake_complete(struct wireguard_peer *peer)
 /* Should be called after an ephemeral key is created, which is before sending a handshake response or after receiving a handshake response. */
 void timers_session_derived(struct wireguard_peer *peer)
 {
-	if (likely(netif_running(peer->device->dev)))
+	if (likely(timers_active(peer)))
 		mod_timer(&peer->timer_zero_key_material, jiffies + (REJECT_AFTER_TIME * 3));
 }
 
 /* Should be called before a packet with authentication -- data, keepalive, either handshake -- is sent, or after one is received. */
 void timers_any_authenticated_packet_traversal(struct wireguard_peer *peer)
 {
-	if (peer->persistent_keepalive_interval && likely(netif_running(peer->device->dev)))
+	if (peer->persistent_keepalive_interval && likely(timers_active(peer)))
 		mod_timer(&peer->timer_persistent_keepalive, slack_time(jiffies + peer->persistent_keepalive_interval));
 }