cifsmount: capture std{err,out} of mount.cifs to log

So it's easier to debug a failed boot.
While at it avoid closing stdin, since a printf might inject
unexpected input into a wrong place (a socket with FD 0).
Redirect stdin from /dev/null instead.

While at it improved error handling a bit (fork, waitpid can fail)

nfsmount: same here

Related: #40554

log.c

@@ -87,3 +87,38 @@ void close_log(void)
 		fclose(logfile);
 	}
 }
+
+int redirect2log(int fd)
+{
+	int rc;
+	if (!logfile) {
+		fprintf(stderr, "%s: log file is not open", __func__);
+		return -1;
+	}
+	rc = dup2(fileno(logfile), fd);
+	if (rc < 0) {
+		log_message("%s: dup2 %d: error: %s", __func__, fd, strerror(errno));
+	}
+	return rc;
+}
+
+int redirect2null(int fd)
+{
+	int nullfd = -1, newfd = -1;
+	nullfd = open("/dev/null", O_RDONLY);
+	if (nullfd < 0) {
+		log_message("%s: open /dev/null: %s", __func__, strerror(errno));
+		goto out;
+	}
+	newfd = dup2(nullfd, fd);
+	if (newfd < 0) {
+		log_message("%s: dup2: %s", __func__, strerror(errno));
+		goto out;
+	}
+out:
+	if (nullfd >= 0) {
+		close(nullfd);
+	}
+	return newfd;
+}
+

log.h

@@ -30,5 +30,12 @@ void vlog_message(const char * s, va_list args);
 void log_perror(char *msg);
 void open_log(void);
 void close_log(void);
+/* @brief Redirect given fd to log
+ *
+ * Useful to capture the output of external utilities
+ */
+int redirect2log(int fd);
+/* @brief Redirect given fd to /dev/null */
+int redirect2null(int fd);
 
 #endif

mount.c

@@ -19,6 +19,7 @@
  *
  */
 
+#include <errno.h>
 #include <stdlib.h>
 #include <limits.h>
 #include <unistd.h>
@@ -133,13 +134,14 @@ static int nfsmount(char *dev, char *location)
 {
 	char spec[PATH_MAX + 17], *sep;
 	struct sockaddr_in saddr;
-	int n, pid, status;
+	pid_t pid;
+	int n, status, ret = -1;
 
 	if ((sep = strchr(dev, ':'))) {
 		*sep = '\0';
 	} else {
 		log_message("nfsmount: directory to mount not in host:dir format");
-		return -1;
+		goto out;
 	}
 
 	saddr.sin_family = AF_INET;
@@ -147,7 +149,7 @@ static int nfsmount(char *dev, char *location)
 		mygethostbyname(dev, &saddr.sin_addr)) {
 		log_message("nfsmount: can't get address for %s", dev);
 		*sep = ':';
-		return -1;
+		goto out;
 	}
 
 	*sep = ':';
@@ -156,17 +158,26 @@ static int nfsmount(char *dev, char *location)
 	strncpy(spec + n, sep, sizeof(spec) - n);
 	log_message("nfsmount %s %s", spec, location);
 
-	if (!(pid = fork())) {
+	pid = fork();
+	if (pid < 0) {
+		log_message("%s: error: fork: %s", __func__, strerror(errno));
+		goto out;
+	} else if (pid == 0) {
 		char * argv[] = {"/bin/nfsmount", spec, location, NULL};
-		close(0);
+		redirect2log(STDOUT_FILENO);
-		close(1);
+		redirect2log(STDERR_FILENO);
-		close(2);
+		redirect2null(STDIN_FILENO);
 		execve(argv[0], argv, NULL);
 		exit(1);
+	} else {
+		if (waitpid(pid, &status, 0) < 0) {
+			log_message("%s: error: waitpid: %s", __func__, strerror(errno));
+			goto out;
+		}
+		ret = (WIFEXITED(status) && !WEXITSTATUS(status)) ? 0 : -1;
 	}
-
+out:
-	waitpid(pid, &status, 0);
+	return ret;
-	return (WIFEXITED(status) && !WEXITSTATUS(status)) ? 0 : -1;
 }
 
 #ifdef ENABLE_CIFS
@@ -174,7 +185,8 @@ static int cifsmount(char *dev, char *location)
 {
 	char spec[PATH_MAX + 19], *sep, *ptr = dev;
 	struct sockaddr_in saddr;
-	int n, pid, status;
+	pid_t pid;
+	int n, status, ret = -1;
 
 	while (*ptr == '/') ptr++;
 
@@ -182,7 +194,7 @@ static int cifsmount(char *dev, char *location)
 		*sep = '\0';
 	} else {
 		log_message("cifsmount: directory to mount not in //host/dir format");
-		return -1;
+		goto out;
 	}
 
 	saddr.sin_family = AF_INET;
@@ -190,7 +202,7 @@ static int cifsmount(char *dev, char *location)
 		mygethostbyname(ptr, &saddr.sin_addr)) {
 		log_message("cifsmount: can't get address for %s", ptr);
 		*sep = '/';
-		return -1;
+		goto out;
 	}
 
 	*sep = '/';
@@ -201,17 +213,26 @@ static int cifsmount(char *dev, char *location)
 	strncpy(spec + n, sep, sizeof(spec) - n);
 	log_message("cifsmount %s %s", spec, location);
 
-	if (!(pid = fork())) {
+	pid = fork();
+	if (pid < 0) {
+		log_message("%s: error: fork: %s", __func__, strerror(errno));
+		goto out;
+	} else if (pid == 0) {
 		char * argv[] = {"/sbin/mount.cifs", spec, location, "-oguest", NULL};
-		close(0);
+		redirect2log(STDOUT_FILENO);
-		close(1);
+		redirect2log(STDERR_FILENO);
-		close(2);
+		redirect2null(STDIN_FILENO);
 		execve(argv[0], argv, NULL);
 		exit(1);
+	} else {
+		if (waitpid(pid, &status, 0) < 0) {
+			log_message("%s: error: waitpid: %s", __func__, strerror(errno));
+			goto out;
+		}
+		ret = (WIFEXITED(status) && !WEXITSTATUS(status)) ? 0 : -1;
 	}
-
+out:
-	waitpid(pid, &status, 0);
+	return ret;
-	return (WIFEXITED(status) && !WEXITSTATUS(status)) ? 0 : -1;
 }
 #endif