hostapd: fix os_daemonize vs starting process race by creating the pid file in the parent

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 38984

package/network/services/hostapd/patches/120-daemonize_fix.patch

@@ -0,0 +1,97 @@
+--- a/src/utils/os_unix.c
++++ b/src/utils/os_unix.c
+@@ -9,6 +9,7 @@
+ #include "includes.h"
+ 
+ #include <time.h>
++#include <fcntl.h>
+ 
+ #ifdef ANDROID
+ #include <sys/capability.h>
+@@ -154,59 +155,46 @@ int os_gmtime(os_time_t t, struct os_tm 
+ 	return 0;
+ }
+ 
+-
+-#ifdef __APPLE__
+-#include <fcntl.h>
+-static int os_daemon(int nochdir, int noclose)
++int os_daemonize(const char *pid_file)
+ {
+-	int devnull;
++	int pid = 0, i, devnull;
+ 
+-	if (chdir("/") < 0)
+-		return -1;
++#if defined(__uClinux__) || defined(__sun__)
++	return -1;
++#else /* defined(__uClinux__) || defined(__sun__) */
+ 
+-	devnull = open("/dev/null", O_RDWR);
+-	if (devnull < 0)
++#ifndef __APPLE__
++	pid = fork();
++	if (pid < 0)
+ 		return -1;
++#endif
+ 
+-	if (dup2(devnull, STDIN_FILENO) < 0) {
+-		close(devnull);
+-		return -1;
++	if (pid > 0) {
++		if (pid_file) {
++			FILE *f = fopen(pid_file, "w");
++			if (f) {
++				fprintf(f, "%u\n", pid);
++				fclose(f);
++			}
++		}
++		_exit(0);
+ 	}
+ 
+-	if (dup2(devnull, STDOUT_FILENO) < 0) {
+-		close(devnull);
++	if (setsid() < 0)
+ 		return -1;
+-	}
+ 
+-	if (dup2(devnull, STDERR_FILENO) < 0) {
+-		close(devnull);
++	if (chdir("/") < 0)
+ 		return -1;
+-	}
+-
+-	return 0;
+-}
+-#else /* __APPLE__ */
+-#define os_daemon daemon
+-#endif /* __APPLE__ */
+ 
+-
+-int os_daemonize(const char *pid_file)
+-{
+-#if defined(__uClinux__) || defined(__sun__)
+-	return -1;
+-#else /* defined(__uClinux__) || defined(__sun__) */
+-	if (os_daemon(0, 0)) {
+-		perror("daemon");
++	devnull = open("/dev/null", O_RDWR);
++	if (devnull < 0)
+ 		return -1;
+-	}
+ 
+-	if (pid_file) {
+-		FILE *f = fopen(pid_file, "w");
+-		if (f) {
+-			fprintf(f, "%u\n", getpid());
+-			fclose(f);
+-		}
+-	}
++	for (i = 0; i <= STDERR_FILENO; i++)
++		dup2(devnull, i);
++
++	if (devnull > 2)
++		close(devnull);
+ 
+ 	return -0;
+ #endif /* defined(__uClinux__) || defined(__sun__) */