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) {
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