svn commit: r353445 - stable/11/lib/libnetgraph

[Eugene Grosbein]

Author: eugen
Date: Fri Oct 11 18:05:06 2019
New Revision: 353445
URL: https://svnweb.freebsd.org/changeset/base/353445

Log:
  MFC r347439 by markj: Atomically update the global gMsgId in libnetgraph.
  
  Otherwise concurrently running threads may inadvertently use the same
  token for different messages.
  
  Preserve the behaviour of disallowing negative message tokens, but allow
  a message token value of zero since this simplifies the code a bit and
  tokens are documented to be non-negative.
  
  PR:		234442

Modified:
  stable/11/lib/libnetgraph/msg.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/lib/libnetgraph/msg.c
==============================================================================
--- stable/11/lib/libnetgraph/msg.c	Fri Oct 11 17:23:23 2019	(r353444)
+++ stable/11/lib/libnetgraph/msg.c	Fri Oct 11 18:05:06 2019	(r353445)
@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <stdarg.h>
+#include <stdatomic.h>
 #include <netgraph/ng_message.h>
 #include <netgraph/ng_socket.h>
 
@@ -51,7 +52,7 @@ __FBSDID("$FreeBSD$");
 #include "internal.h"
 
 /* Next message token value */
-static int	gMsgId;
+static _Atomic(unsigned int) gMsgId;
 
 /* For delivering both messages and replies */
 static int	NgDeliverMsg(int cs, const char *path,
@@ -72,9 +73,7 @@ NgSendMsg(int cs, const char *path,
 	memset(&msg, 0, sizeof(msg));
 	msg.header.version = NG_VERSION;
 	msg.header.typecookie = cookie;
-	if (++gMsgId < 0)
-		gMsgId = 1;
-	msg.header.token = gMsgId;
+	msg.header.token = atomic_fetch_add(&gMsgId, 1) & INT_MAX;
 	msg.header.flags = NGF_ORIG;
 	msg.header.cmd = cmd;
 	snprintf((char *)msg.header.cmdstr, NG_CMDSTRSIZ, "cmd%d", cmd);
@@ -143,9 +142,7 @@ NgSendAsciiMsg(int cs, const char *path, const char *f
 
 	/* Now send binary version */
 	binary = (struct ng_mesg *)reply->data;
-	if (++gMsgId < 0)
-		gMsgId = 1;
-	binary->header.token = gMsgId;
+	binary->header.token = atomic_fetch_add(&gMsgId, 1) & INT_MAX;
 	binary->header.version = NG_VERSION;
 	if (NgDeliverMsg(cs,
 	    path, binary, binary->data, binary->header.arglen) < 0) {