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The pidfile_open(3) is going to be fixed to set close-on-exec in order

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not to leak the descriptor after exec(3). This raises the issue for
daemon(3) of the pidfile lock to be lost when the child process
executes.

To solve this and also to have the pidfile cleaned up when the program
exits, if a pidfile is specified, spawn a child to exec the command
and wait in the parent keeping the pidfile locked until the child
process exits and remove the file.

Reported by:	Andrey Zonov <andrey zonov org>
Suggested by:	pjd
Reviewed by:	pjd
MFC after:	2 weeks
This commit is contained in:
Mikolaj Golub 2012-02-19 10:20:37 +00:00
parent 3f07025a76
commit 2ad4302785
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=231909
2 changed files with 58 additions and 26 deletions
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20
usr.sbin/daemon/daemon.8
View File

@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd March 19, 2007
.Dd February 19, 2012
.Dt DAEMON 8
.Os
.Sh NAME
@ -59,14 +59,18 @@ Write the ID of the created process into the
using the
.Xr pidfile 3
functionality.
If the
The program is executed in a spawned child process while the
.Nm
waits until it terminates to keep the
.Ar file
locked and removes it after the process exits.
The
.Ar file
owner is the user who runs the
.Nm
regardless of whether the
.Fl u
option is used, either the pidfile needs to have been pre-created
with appropriate ownership and permissions, or the directory to contain
the pidfile must be writable by the specified user.
Note, that the file will be created shortly before the process is
actually executed, and will remain after the process exits (although
it will be removed if the execution fails).
option is used or not.
.It Fl u Ar user
Login name of the user to execute the program under.
Requires adequate superuser privileges.

64
usr.sbin/daemon/daemon.c
View File

@ -32,6 +32,7 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/wait.h>
#include <err.h>
#include <errno.h>
@ -43,15 +44,16 @@ __FBSDID("$FreeBSD$");
#include <unistd.h>
static void restrict_process(const char *);
static void wait_child(pid_t pid);
static void usage(void);
int
main(int argc, char *argv[])
{
struct pidfh *pfh = NULL;
int ch, nochdir, noclose, errcode;
int ch, nochdir, noclose;
const char *pidfile, *user;
pid_t otherpid;
pid_t otherpid, pid;
nochdir = noclose = 1;
pidfile = user = NULL;
@ -79,14 +81,12 @@ main(int argc, char *argv[])
if (argc == 0)
usage();
if (user != NULL)
restrict_process(user);
pfh = NULL;
/*
* Try to open the pidfile before calling daemon(3),
* to be able to report the error intelligently
*/
if (pidfile) {
if (pidfile != NULL) {
pfh = pidfile_open(pidfile, 0600, &otherpid);
if (pfh == NULL) {
if (errno == EEXIST) {
@ -100,22 +100,37 @@ main(int argc, char *argv[])
if (daemon(nochdir, noclose) == -1)
err(1, NULL);
/* Now that we are the child, write out the pid */
if (pidfile)
pid = 0;
if (pidfile != NULL) {
/*
* Spawn a child to exec the command, so in the parent
* we could wait for it to exit and remove pidfile.
*/
pid = fork();
if (pid == -1) {
pidfile_remove(pfh);
err(1, "fork");
}
}
if (pid == 0) {
/* Now that we are the child, write out the pid. */
pidfile_write(pfh);
execvp(argv[0], argv);
if (user != NULL)
restrict_process(user);
/*
* execvp() failed -- unlink pidfile if any, and
* report the error
*/
errcode = errno; /* Preserve errcode -- unlink may reset it */
if (pidfile)
pidfile_remove(pfh);
execvp(argv[0], argv);
/* The child is now running, so the exit status doesn't matter. */
errc(1, errcode, "%s", argv[0]);
/*
* execvp() failed -- report the error. The child is
* now running, so the exit status doesn't matter.
*/
err(1, "%s", argv[0]);
}
setproctitle("%s[%d]", argv[0], pid);
wait_child(pid);
pidfile_remove(pfh);
exit(0); /* Exit status does not matter. */
}
static void
@ -131,6 +146,19 @@ restrict_process(const char *user)
errx(1, "failed to set user environment");
}
static void
wait_child(pid_t pid)
{
int status;
while (waitpid(pid, &status, 0) == -1) {
if (errno != EINTR) {
warn("waitpid");
break;
}
}
}
static void
usage(void)
{