Limit the number of simultanious children

Make sure minidlna cannot fork more than 5 children, to avoid becoming a
fork bomb.

Reported-by: Rinat Ibragimov <ibragimovrinat@mail.ru>
This commit is contained in:
Benoît Knecht 2013-06-13 23:23:21 +02:00
parent 862f6b986c
commit 3995cbdac4
5 changed files with 117 additions and 75 deletions

View File

@ -6,7 +6,7 @@ sbin_PROGRAMS = minidlnad
check_PROGRAMS = testupnpdescgen
minidlnad_SOURCES = minidlna.c upnphttp.c upnpdescgen.c upnpsoap.c \
upnpreplyparse.c minixml.c clients.c \
getifaddr.c daemonize.c upnpglobalvars.c \
getifaddr.c process.c upnpglobalvars.c \
options.c minissdp.c uuid.c upnpevents.c \
sql.c utils.c metadata.c scanner.c inotify.c \
tivo_utils.c tivo_beacon.c tivo_commands.c \

View File

@ -86,7 +86,7 @@
#include "utils.h"
#include "minissdp.h"
#include "minidlnatypes.h"
#include "daemonize.h"
#include "process.h"
#include "upnpevents.h"
#include "scanner.h"
#include "inotify.h"
@ -155,14 +155,6 @@ sigterm(int sig)
quitting = 1;
}
static void
sigchld(int sig)
{
if (!scanning)
signal(SIGCHLD, SIG_IGN);
waitpid(-1, NULL, WNOHANG);
}
static void
sighup(int sig)
{
@ -369,9 +361,9 @@ rescan:
#if USE_FORK
scanning = 1;
sqlite3_close(db);
*scanner_pid = fork();
*scanner_pid = process_fork();
open_db(&db);
if (!(*scanner_pid)) /* child (scanner) process */
if (*scanner_pid == 0) /* child (scanner) process */
{
start_scanner();
sqlite3_close(db);
@ -379,6 +371,10 @@ rescan:
freeoptions();
exit(EXIT_SUCCESS);
}
else if (*scanner_pid < 0)
{
start_scanner();
}
#else
start_scanner();
#endif
@ -884,7 +880,7 @@ init(int argc, char **argv)
}
else
{
pid = daemonize();
pid = process_daemonize();
#ifdef READYNAS
unlink("/ramfs/.upnp-av_scan");
path = "/var/log/upnp-av.log";
@ -897,7 +893,7 @@ init(int argc, char **argv)
}
log_init(path, log_level);
if (checkforrunning(pidfilename) < 0)
if (process_check_if_running(pidfilename) < 0)
{
DPRINTF(E_ERROR, L_GENERAL, "MiniDLNA is already running. EXITING.\n");
return 1;
@ -923,6 +919,9 @@ init(int argc, char **argv)
DPRINTF(E_FATAL, L_GENERAL, "Failed to set %s handler. EXITING.\n", "SIGPIPE");
if (signal(SIGHUP, &sighup) == SIG_ERR)
DPRINTF(E_FATAL, L_GENERAL, "Failed to set %s handler. EXITING.\n", "SIGHUP");
sa.sa_handler = process_handle_child_termination;
if (sigaction(SIGCHLD, &sa, NULL))
DPRINTF(E_FATAL, L_GENERAL, "Failed to set %s handler. EXITING.\n", "SIGCHLD");
if (writepidfile(pidfilename, pid, uid) != 0)
pidfilename = NULL;
@ -989,7 +988,6 @@ main(int argc, char **argv)
ret = -1;
}
check_db(db, ret, &scanner_pid);
signal(SIGCHLD, &sigchld);
#ifdef HAVE_INOTIFY
if( GETFLAG(INOTIFY_MASK) )
{

View File

@ -1,7 +1,8 @@
/* MiniUPnP project
* http://miniupnp.free.fr/ or http://miniupnp.tuxfamily.org/
/* Process handling
*
* Copyright © 2006, Thomas Bernard
* Copyright © 2013, Benoît Knecht <benoit.knecht@fsfe.org>
*
* Copyright (c) 2006, Thomas Bernard
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -35,48 +36,74 @@
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <sys/wait.h>
#include "daemonize.h"
#include "process.h"
#include "config.h"
#include "log.h"
static const int max_number_of_children = 5;
static int number_of_children = 0;
pid_t
process_fork(void)
{
if (number_of_children >= max_number_of_children)
{
errno = EAGAIN;
return -1;
}
pid_t pid = fork();
if (pid > 0)
++number_of_children;
return pid;
}
void
process_handle_child_termination(int signal)
{
waitpid(-1, NULL, WNOHANG);
--number_of_children;
}
int
daemonize(void)
process_daemonize(void)
{
int pid;
#ifndef USE_DAEMON
int i;
switch(fork())
switch(process_fork())
{
/* fork error */
case -1:
perror("fork()");
exit(1);
/* child process */
case 0:
/* obtain a new process group */
if( (pid = setsid()) < 0)
{
perror("setsid()");
/* fork error */
case -1:
perror("fork()");
exit(1);
}
/* close all descriptors */
for (i=getdtablesize();i>=0;--i) close(i);
/* child process */
case 0:
/* obtain a new process group */
if( (pid = setsid()) < 0)
{
perror("setsid()");
exit(1);
}
i = open("/dev/null",O_RDWR); /* open stdin */
dup(i); /* stdout */
dup(i); /* stderr */
/* close all descriptors */
for (i=getdtablesize();i>=0;--i) close(i);
umask(027);
chdir("/");
i = open("/dev/null",O_RDWR); /* open stdin */
dup(i); /* stdout */
dup(i); /* stderr */
break;
/* parent process */
default:
exit(0);
umask(027);
chdir("/");
break;
/* parent process */
default:
exit(0);
}
#else
if( daemon(0, 0) < 0 )
@ -87,7 +114,7 @@ daemonize(void)
}
int
checkforrunning(const char * fname)
process_check_if_running(const char *fname)
{
char buffer[64];
int pidfile;
@ -117,4 +144,3 @@ checkforrunning(const char * fname)
return 0;
}

View File

@ -1,7 +1,7 @@
/* MiniUPnP project
* http://miniupnp.free.fr/ or http://miniupnp.tuxfamily.org/
/* Process handling
*
* Copyright © 2013, Benoît Knecht <benoit.knecht@fsfe.org>
*
* Copyright (c) 2006, Thomas Bernard
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -26,24 +26,41 @@
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __DAEMONIZE_H__
#define __DAEMONIZE_H__
#ifndef __PROCESS_H__
#define __PROCESS_H__
#include "config.h"
#include <unistd.h>
/* daemonize()
* "fork" to background, detach from terminal, etc...
* returns: pid of the daemon, exits upon failure */
int
daemonize(void);
/**
* Fork a new child (just like fork()) but keep track of how many childs are
* already running, and refuse fo fork if there are too many.
* @return -1 if it couldn't fork, 0 in the child process, the pid of the
* child process in the parent process.
*/
pid_t process_fork(void);
/* checkforrunning()
* check for another instance running
* returns: 0 only instance
* -1 invalid filename
* -2 another instance running */
int
checkforrunning(const char * fname);
/**
* Handler to be called upon receiving SIGCHLD. This signal is received by the
* parent process when a child terminates, and this handler updates the number
* of running childs accordingly.
* @param signal The signal number.
*/
void process_handle_child_termination(int signal);
#endif
/**
* Daemonize the current process by forking itself and redirecting standard
* input, standard output and standard error to /dev/null.
* @return The pid of the process.
*/
int process_daemonize(void);
/**
* Check if the process corresponding to the pid found in the pid file is
* running.
* @param fname The path to the pid file.
* @return 0 if no other instance is running, -1 if the file name is invalid,
* -2 if another instance is running.
*/
int process_check_if_running(const char *fname);
#endif // __PROCESS_H__

View File

@ -78,6 +78,7 @@
#include "tivo_utils.h"
#include "tivo_commands.h"
#include "clients.h"
#include "process.h"
#include "sendfile.h"
@ -1574,8 +1575,8 @@ SendResp_resizedimg(struct upnphttp * h, char * object)
#if USE_FORK
pid_t newpid = 0;
newpid = fork();
if( newpid )
newpid = process_fork();
if( newpid > 0 )
{
CloseSocket_upnphttp(h);
goto resized_error;
@ -1716,7 +1717,7 @@ SendResp_resizedimg(struct upnphttp * h, char * object)
resized_error:
sqlite3_free_table(result);
#if USE_FORK
if( !newpid )
if( newpid == 0 )
_exit(0);
#endif
}
@ -1809,8 +1810,8 @@ SendResp_dlnafile(struct upnphttp *h, char *object)
sqlite3_free_table(result);
}
#if USE_FORK
newpid = fork();
if( newpid )
newpid = process_fork();
if( newpid > 0 )
{
CloseSocket_upnphttp(h);
goto error;
@ -1951,7 +1952,7 @@ SendResp_dlnafile(struct upnphttp *h, char *object)
CloseSocket_upnphttp(h);
error:
#if USE_FORK
if( !newpid )
if( newpid == 0 )
_exit(0);
#endif
return;