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bring std(in|out|err) fd's in a sane state

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If the kernel forks us as an usermodhelper, we don't have any of
the standard fd's and the first open() will start with fd=0.
This is inherited to all forked childs and confuses later forked
helpers where we want to read from a pipe connected to the helpers
stdout/stderr.

  # ls -l /proc/$(pidof udevd)/fd
  total 6
  dr-x------  2 root root  0 2005-08-18 12:44 .
  dr-xr-xr-x  4 root root  0 2005-08-18 12:44 ..
  lrwx------  1 root root 64 2005-08-18 12:44 0 -> /dev/null
  lrwx------  1 root root 64 2005-08-18 12:44 1 -> socket:[1274617]
  lr-x------  1 root root 64 2005-08-18 12:44 2 -> pipe:[1274618]
  l-wx------  1 root root 64 2005-08-18 12:44 3 -> pipe:[1274618]
  lrwx------  1 root root 64 2005-08-18 12:44 4 -> socket:[1274619]
  lrwx------  1 root root 64 2005-08-18 12:44 5 -> socket:[1274620]

Ouch! This will obviously not redirect sterr, it will kill the pipe
we established between the parent and the child:

  devnull = open("/dev/null", O_RDWR);
  dup2(devnull, STDERR_FILENO);

Signed-off-by: Kay Sievers <kay.sievers@suse.de>
This commit is contained in:
Kay Sievers 2005-08-18 13:07:15 +02:00
parent e331c54dc5
commit 3f9f8de4de
2 changed files with 32 additions and 10 deletions
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16
udev.c
View File

@ -72,6 +72,7 @@ int main(int argc, char *argv[], char *envp[])
const char *devpath;
const char *subsystem;
struct sigaction act;
int devnull;
int retval = -EINVAL;
if (argc == 2 && strcmp(argv[1], "-V") == 0) {
@ -79,7 +80,22 @@ int main(int argc, char *argv[], char *envp[])
exit(0);
}
/* set std fd's to /dev/null, if the kernel forks us, we don't have them at all */
devnull = open("/dev/null", O_RDWR);
if (devnull >= 0) {
if (devnull != STDIN_FILENO)
dup2(devnull, STDIN_FILENO);
if (devnull != STDOUT_FILENO)
dup2(devnull, STDOUT_FILENO);
if (devnull != STDERR_FILENO)
dup2(devnull, STDERR_FILENO);
if (devnull > STDERR_FILENO)
close(devnull);
}
logging_init("udev");
if (devnull < 0)
err("fatal, could not open /dev/null");
udev_init_config();
dbg("version %s", UDEV_VERSION);

26
udevd.c
View File

@ -777,7 +777,23 @@ int main(int argc, char *argv[], char *envp[])
int daemonize = 0;
int i;
/* set std fd's to /dev/null, if the kernel forks us, we don't have them at all */
devnull = open("/dev/null", O_RDWR);
if (devnull >= 0) {
if (devnull != STDIN_FILENO)
dup2(devnull, STDIN_FILENO);
if (devnull != STDOUT_FILENO)
dup2(devnull, STDOUT_FILENO);
if (devnull != STDERR_FILENO)
dup2(devnull, STDERR_FILENO);
if (devnull > STDERR_FILENO)
close(devnull);
}
logging_init("udevd");
if (devnull < 0)
err("fatal, could not open /dev/null");
udev_init_config();
dbg("version %s", UDEV_VERSION);
@ -825,16 +841,6 @@ int main(int argc, char *argv[], char *envp[])
/* set a reasonable scheduling priority for the daemon */
setpriority(PRIO_PROCESS, 0, UDEVD_PRIORITY);
/* Set fds to dev/null */
devnull = open( "/dev/null", O_RDWR );
if (devnull > 0) {
dup2(devnull, STDIN_FILENO);
dup2(devnull, STDOUT_FILENO);
dup2(devnull, STDERR_FILENO);
close(devnull);
} else
err("error opening /dev/null %s", strerror(errno));
/* setup signal handler pipe */
retval = pipe(pipefds);
if (retval < 0) {