From: Todd C. Miller <Todd.Miller@courtesan.com>
Date: Wed, 12 May 2010 15:13:40 +0000 (-0400)
Subject: Avoid a potential race condition if SIGCHLD is received immediately
X-Git-Tag: SUDO_1_8_0~639
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=396317ffe9203fe9ba908ee1f52d8beb4b9a789f;p=sudo

Avoid a potential race condition if SIGCHLD is received immediately
before we call select().
---

diff --git a/src/script.c b/src/script.c
index 18fc0f04b..e3425cc14 100644
--- a/src/script.c
+++ b/src/script.c
@@ -766,6 +766,8 @@ script_execve(struct command_details *details, char *argv[], char *envp[],
 	    }
 	}
 
+	if (recvsig[SIGCHLD])
+	    continue;
 	nready = select(maxfd + 1, fdsr, fdsw, NULL, NULL);
 	if (nready == -1) {
 	    if (errno == EINTR)
@@ -1050,7 +1052,7 @@ script_child(const char *path, char *argv[], char *envp[], int backchannel, int
     zero_bytes(&cstat, sizeof(cstat));
     for (;;) {
 	/* Read child status */
-	while (recvsig[SIGCHLD]) {
+	if (recvsig[SIGCHLD]) {
 	    recvsig[SIGCHLD] = FALSE;
 	    /* read child status and relay to parent */
 	    do {
@@ -1087,6 +1089,9 @@ script_child(const char *path, char *argv[], char *envp[], int backchannel, int
 	if (errpipe[0] != -1)
 	    FD_SET(errpipe[0], fdsr);
 	maxfd = MAX(errpipe[0], backchannel);
+
+	if (recvsig[SIGCHLD])
+	    continue;
 	n = select(maxfd + 1, fdsr, NULL, NULL, NULL);
 	if (n == -1) {
 	    if (errno == EINTR)