From: Roy Marples <roy@marples.name>
Date: Sat, 2 Feb 2008 19:17:08 +0000 (+0000)
Subject: Block signals to avoid potential signal racing on BSD using fork.
X-Git-Tag: v3.2.3~40
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=76ef136f1d0b2c1252da87a3c39e489e579f7eb0;p=thirdparty%2Fdhcpcd.git

Block signals to avoid potential signal racing on BSD using fork.
---

diff --git a/configure.c b/configure.c
index 71282bb7..6372ee55 100644
--- a/configure.c
+++ b/configure.c
@@ -46,11 +46,14 @@
 #include <unistd.h>
 
 #ifndef BSD
-#define HAVE_POSIX_SPAWN
+# define HAVE_POSIX_SPAWN
 #endif
 
 #ifdef HAVE_POSIX_SPAWN
-#include <spawn.h>
+# include <spawn.h>
+extern char **environ;
+#else
+# include <signal.h>
 #endif
 
 #include "config.h"
@@ -65,7 +68,9 @@
 #include "logger.h"
 #include "socket.h"
 
-extern char **environ;
+#ifndef HAVE_POSIX_SPAWN
+#include "signal.h"
+#endif
 
 static int file_in_path (const char *file)
 {
@@ -103,6 +108,8 @@ static int exec_cmd (const char *cmd, const char *args, ...)
 	int ret;
 #ifndef HAVE_POSIX_SPAWN
 	pid_t pid;
+	sigset_t full;
+	sigset_t old;
 #endif
 
 	va_start (va, args);
@@ -128,15 +135,28 @@ static int exec_cmd (const char *cmd, const char *args, ...)
 		ret = -1;
 	}
 #else
-	if ((pid = vfork ()) == 0) {
-		if (execvp (cmd, argv) && errno != ENOENT)
-			logger (LOG_ERR, "error executing \"%s\": %s",
-				cmd, strerror (errno));
-		_exit (0);
-	} else if (pid == -1) {
-		logger (LOG_ERR, "vfork: %s", strerror (errno));
-		ret = -1;
+	/* OK, we need to block signals */
+	sigfillset (&full);
+	sigprocmask (SIG_SETMASK, &full, &old);
+
+	switch (pid = fork()) {
+		case -1:
+			logger (LOG_ERR, "vfork: %s", strerror (errno));
+			ret = -1;
+			break;
+		case 0:
+			/* Reset signals and clear block */
+			signal_reset ();
+			sigprocmask (SIG_SETMASK, &old, NULL);
+			if (execvp (cmd, argv) && errno != ENOENT)
+				logger (LOG_ERR, "error executing \"%s\": %s",
+					cmd, strerror (errno));
+			_exit (0);
+			/* NOTREACHED */
 	}
+
+	/* Restore our signals */
+	sigprocmask (SIG_SETMASK, &old, NULL);
 #endif
 
 	free (argv);
diff --git a/signal.c b/signal.c
index a61cb234..d38efb47 100644
--- a/signal.c
+++ b/signal.c
@@ -163,3 +163,21 @@ int signal_setup (void)
 
 	return (0);
 }
+
+int signal_reset (void)
+{
+	struct sigaction sa;
+	unsigned int i;
+
+	memset (&sa, 0, sizeof (sa));
+	sa.sa_handler = SIG_DFL;
+	sigemptyset (&sa.sa_mask);
+
+	for (i = 0; i < sizeof (handle_sigs) / sizeof (handle_sigs[0]); i++)
+		if (sigaction (handle_sigs[i], &sa, NULL) == -1) {
+			logger (LOG_ERR, "sigaction: %s", strerror (errno));
+			return (-1);
+		}
+
+	return (0);
+}
diff --git a/signal.h b/signal.h
index eccec518..d7baa6e0 100644
--- a/signal.h
+++ b/signal.h
@@ -29,6 +29,7 @@
 #define SIGNAL_H
 
 int signal_setup (void);
+int signal_reset (void);
 int signal_fd_set (fd_set *rset, int fd);
 int signal_exists (const fd_set *rset);
 int signal_read (fd_set *rset);