File 0011-bgpd-avoid-notify-race-between-io-and-main... of Package frr.26974

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File 0011-bgpd-avoid-notify-race-between-io-and-main-pthreads.patch of Package frr.26974

From d6bbc7e4545ff8a766f3863764e3d0aa968e1932 Mon Sep 17 00:00:00 2001
From: Mark Stapp <mstapp@nvidia.com>
Date: Thu, 8 Sep 2022 16:14:36 -0400
References: CVE-2022-37035,bsc#1202085
Upstream: yes
Subject: [PATCH] bgpd: avoid notify race between io and main pthreads

The "bgp_notify_" apis in bgp_packet.c generate a notification
to a peer, usually during error handling. The io pthread wants
to send notifications in a couple of cases during early
received-packet validation - but the existing api interacts
with the peer struct itself, and that's not safe.

Add a new api for use by the io pthread, and adjust the main
notify api so that it can avoid touching the peer struct.

Signed-off-by: Mark Stapp <mstapp@nvidia.com>

diff --git a/bgpd/bgp_io.c b/bgpd/bgp_io.c
index ab50c545b5..03b2086559 100644
--- a/bgpd/bgp_io.c
+++ b/bgpd/bgp_io.c
@@ -38,7 +38,7 @@
 #include "bgpd/bgp_debug.h"	// for bgp_debug_neighbor_events, bgp_type_str
 #include "bgpd/bgp_errors.h"	// for expanded error reference information
 #include "bgpd/bgp_fsm.h"	// for BGP_EVENT_ADD, bgp_event
-#include "bgpd/bgp_packet.h"	// for bgp_notify_send_with_data, bgp_notify...
+#include "bgpd/bgp_packet.h"	// for bgp_notify_io_invalid...
 #include "bgpd/bgpd.h"		// for peer, BGP_MARKER_SIZE, bgp_master, bm
 /* clang-format on */
 
@@ -523,8 +523,8 @@ static bool validate_header(struct peer *peer)
 		return false;
 
 	if (memcmp(m_correct, m_rx, BGP_MARKER_SIZE) != 0) {
-		bgp_notify_send(peer, BGP_NOTIFY_HEADER_ERR,
-				BGP_NOTIFY_HEADER_NOT_SYNC);
+		bgp_notify_io_invalid(peer, BGP_NOTIFY_HEADER_ERR,
+				      BGP_NOTIFY_HEADER_NOT_SYNC, NULL, 0);
 		return false;
 	}
 
@@ -544,9 +544,8 @@ static bool validate_header(struct peer *peer)
 			zlog_debug("%s unknown message type 0x%02x", peer->host,
 				   type);
 
-		bgp_notify_send_with_data(peer, BGP_NOTIFY_HEADER_ERR,
-					  BGP_NOTIFY_HEADER_BAD_MESTYPE, &type,
-					  1);
+		bgp_notify_io_invalid(peer, BGP_NOTIFY_HEADER_ERR,
+				      BGP_NOTIFY_HEADER_BAD_MESTYPE, &type, 1);
 		return false;
 	}
 
@@ -571,9 +570,9 @@ static bool validate_header(struct peer *peer)
 
 		uint16_t nsize = htons(size);
 
-		bgp_notify_send_with_data(peer, BGP_NOTIFY_HEADER_ERR,
-					  BGP_NOTIFY_HEADER_BAD_MESLEN,
-					  (unsigned char *)&nsize, 2);
+		bgp_notify_io_invalid(peer, BGP_NOTIFY_HEADER_ERR,
+				      BGP_NOTIFY_HEADER_BAD_MESLEN,
+				      (unsigned char *)&nsize, 2);
 		return false;
 	}
 
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 4f7e7c8cba..28ed541a4a 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -674,8 +674,9 @@ static void bgp_write_notify(struct peer *peer)
  * @param data      Data portion
  * @param datalen   length of data portion
  */
-void bgp_notify_send_with_data(struct peer *peer, uint8_t code,
-			       uint8_t sub_code, uint8_t *data, size_t datalen)
+static void bgp_notify_send_internal(struct peer *peer, uint8_t code,
+				     uint8_t sub_code, uint8_t *data,
+				     size_t datalen, bool use_curr)
 {
 	struct stream *s;
 
@@ -707,8 +708,11 @@ void bgp_notify_send_with_data(struct peer *peer, uint8_t code,
 	 * If possible, store last packet for debugging purposes. This check is
 	 * in place because we are sometimes called with a doppelganger peer,
 	 * who tends to have a plethora of fields nulled out.
+	 *
+	 * Some callers should not attempt this - the io pthread for example
+	 * should not touch internals of the peer struct.
 	 */
-	if (peer->curr) {
+	if (use_curr && peer->curr) {
 		size_t packetsize = stream_get_endp(peer->curr);
 		assert(packetsize <= sizeof(peer->last_reset_cause));
 		memcpy(peer->last_reset_cause, peer->curr->data, packetsize);
@@ -791,7 +795,27 @@ void bgp_notify_send_with_data(struct peer *peer, uint8_t code,
  */
 void bgp_notify_send(struct peer *peer, uint8_t code, uint8_t sub_code)
 {
-	bgp_notify_send_with_data(peer, code, sub_code, NULL, 0);
+	bgp_notify_send_internal(peer, code, sub_code, NULL, 0, true);
+}
+
+/*
+ * Enqueue notification; called from the main pthread, peer object access is ok.
+ */
+void bgp_notify_send_with_data(struct peer *peer, uint8_t code,
+			       uint8_t sub_code, uint8_t *data, size_t datalen)
+{
+	bgp_notify_send_internal(peer, code, sub_code, data, datalen, true);
+}
+
+/*
+ * For use by the io pthread, queueing a notification but avoiding access to
+ * the peer object.
+ */
+void bgp_notify_io_invalid(struct peer *peer, uint8_t code, uint8_t sub_code,
+			   uint8_t *data, size_t datalen)
+{
+	/* Avoid touching the peer object */
+	bgp_notify_send_internal(peer, code, sub_code, data, datalen, false);
 }
 
 /*
diff --git a/bgpd/bgp_packet.h b/bgpd/bgp_packet.h
index e83f7d950c..62028175d1 100644
--- a/bgpd/bgp_packet.h
+++ b/bgpd/bgp_packet.h
@@ -62,6 +62,8 @@ extern void bgp_open_send(struct peer *);
 extern void bgp_notify_send(struct peer *, uint8_t, uint8_t);
 extern void bgp_notify_send_with_data(struct peer *, uint8_t, uint8_t,
 				      uint8_t *, size_t);
+void bgp_notify_io_invalid(struct peer *peer, uint8_t code, uint8_t sub_code,
+			   uint8_t *data, size_t datalen);
 extern void bgp_route_refresh_send(struct peer *, afi_t, safi_t, uint8_t,
 				   uint8_t, int);
 extern void bgp_capability_send(struct peer *, afi_t, safi_t, int, int);
-- 
2.35.3

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