Date: Fri, 10 May 2019 16:43:47 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r347439 - head/lib/libnetgraph Message-ID: <201905101643.x4AGhlja087906@repo.freebsd.org>
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Author: markj Date: Fri May 10 16:43:47 2019 New Revision: 347439 URL: https://svnweb.freebsd.org/changeset/base/347439 Log: 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 Reported and tested by: eugen MFC after: 1 month Sponsored by: The FreeBSD Foundation Modified: head/lib/libnetgraph/msg.c Modified: head/lib/libnetgraph/msg.c ============================================================================== --- head/lib/libnetgraph/msg.c Fri May 10 16:41:33 2019 (r347438) +++ head/lib/libnetgraph/msg.c Fri May 10 16:43:47 2019 (r347439) @@ -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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