shithub: riscv

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ref: 8d2b84747b1cbc54d6f23cc461d3ef838c1dfec9
parent: 2ca3934809cc51fed6a386eb13f67f08fd89fdf2
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Fri Jan 5 01:46:35 EST 2024

ip/ppp: fix race condition with rfork()

ipinprocpid is static so shared with parent and child,
so we need a temporary variable on the local stack
to properly assign ipinprocpid.

--- a/sys/src/cmd/ip/ppp/ppp.c
+++ b/sys/src/cmd/ip/ppp/ppp.c
@@ -1640,7 +1640,7 @@
 ipopen(PPP *ppp)
 {
 	static int ipinprocpid;
-	int n, cfd, fd;
+	int n, cfd, fd, pid;
 	char path[128];
 	char buf[128];
 
@@ -1676,7 +1676,7 @@
 		close(cfd);
 
 		ppp->ipfd = fd;
-		switch(ipinprocpid = rfork(RFPROC|RFMEM|RFNOWAIT)){
+		switch(pid = rfork(RFPROC|RFMEM|RFNOWAIT)){
 		case -1:
 			terminate(ppp, "forking ipinproc", 1);
 		case 0:
@@ -1684,6 +1684,7 @@
 			terminate(ppp, "ipinproc", 0);
 			exits(nil);
 		}
+		ipinprocpid = pid;
 
 		if(validv4(ppp->local)){
 			if(!validv4(ppp->remote))